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	$100.43	4.656%	$105.106	$105.11	$105.10	$105.10
Purchase #2	$131.60	7.155%	$141.016	$141.02	$141.00	$141.00
Purchase #3	$198.70	6.623%	$211.8599	$211.86	$211.85	$211.90
Purchase #4	$204.29	13.331%	$231.5239	$231.52	$231.50	$231.50
Purchase #5	$51.85	5.528%	$54.7163	$54.72	$54.70	$54.70
Purchase #6	$69.62	12.694%	$78.4576	$78.46	$78.45	$78.50
Purchase #7	$155.82	9.787%	$171.0701	$171.07	$171.05	$171.10
7 purchase totals =	$912.31		$993.7498	$993.76	$993.65	$993.80