Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$235.39	12.183%	$264.0676	$264.07	$264.05	$264.10
Purchase #2	$168.69	12.621%	$189.9804	$189.98	$190.00	$190.00
Purchase #3	$186.45	6.439%	$198.4555	$198.46	$198.45	$198.50
Purchase #4	$162.32	5.434%	$171.1405	$171.14	$171.15	$171.10
Purchase #5	$191.93	10.547%	$212.1729	$212.17	$212.15	$212.20
Purchase #6	$147.65	5.455%	$155.7043	$155.70	$155.70	$155.70
Purchase #7	$126.80	12.256%	$142.3406	$142.34	$142.35	$142.30
7 purchase totals =	$1,219.23		$1,333.8618	$1,333.86	$1,333.85	$1,333.90