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	$185.39	3.123%	$191.1797	$191.18	$191.20	$191.20
Purchase #2	$196.83	7.693%	$211.9721	$211.97	$211.95	$212.00
Purchase #3	$119.57	10.585%	$132.2265	$132.23	$132.25	$132.20
Purchase #4	$250.89	7.171%	$268.8813	$268.88	$268.90	$268.90
Purchase #5	$79.56	8.764%	$86.5326	$86.53	$86.55	$86.50
Purchase #6	$35.41	6.281%	$37.6341	$37.63	$37.65	$37.60
Purchase #7	$68.47	9.478%	$74.9596	$74.96	$74.95	$75.00
7 purchase totals =	$936.12		$1,003.3859	$1,003.38	$1,003.45	$1,003.40