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	$209.33	6.337%	$222.5952	$222.60	$222.60	$222.60
Purchase #2	$156.26	6.822%	$166.9201	$166.92	$166.90	$166.90
Purchase #3	$240.60	5.476%	$253.7753	$253.78	$253.80	$253.80
Purchase #4	$88.48	10.650%	$97.9031	$97.90	$97.90	$97.90
Purchase #5	$228.90	11.324%	$254.8206	$254.82	$254.80	$254.80
Purchase #6	$93.73	4.802%	$98.2309	$98.23	$98.25	$98.20
Purchase #7	$45.89	4.867%	$48.1235	$48.12	$48.10	$48.10
7 purchase totals =	$1,063.19		$1,142.3687	$1,142.37	$1,142.35	$1,142.30