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	$56.63	6.403%	$60.256	$60.26	$60.25	$60.30
Purchase #2	$26.56	6.675%	$28.3329	$28.33	$28.35	$28.30
Purchase #3	$47.51	11.728%	$53.082	$53.08	$53.10	$53.10
Purchase #4	$199.94	10.536%	$221.0057	$221.01	$221.00	$221.00
Purchase #5	$150.72	9.568%	$165.1409	$165.14	$165.15	$165.10
Purchase #6	$211.43	13.798%	$240.6031	$240.60	$240.60	$240.60
Purchase #7	$73.78	4.561%	$77.1451	$77.15	$77.15	$77.10
7 purchase totals =	$766.57		$845.5657	$845.57	$845.60	$845.50