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	$168.91	9.358%	$184.7166	$184.72	$184.70	$184.70
Purchase #2	$209.86	6.111%	$222.6845	$222.68	$222.70	$222.70
Purchase #3	$130.55	5.239%	$137.3895	$137.39	$137.40	$137.40
Purchase #4	$78.99	3.857%	$82.0366	$82.04	$82.05	$82.00
Purchase #5	$106.34	4.400%	$111.019	$111.02	$111.00	$111.00
Purchase #6	$89.76	6.711%	$95.7838	$95.78	$95.80	$95.80
Purchase #7	$155.78	12.109%	$174.6434	$174.64	$174.65	$174.60
7 purchase totals =	$940.19		$1,008.2734	$1,008.27	$1,008.30	$1,008.20