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	$151.67	3.218%	$156.5507	$156.55	$156.55	$156.60
Purchase #2	$118.96	6.340%	$126.5021	$126.50	$126.50	$126.50
Purchase #3	$233.37	3.802%	$242.2427	$242.24	$242.25	$242.20
Purchase #4	$99.36	4.784%	$104.1134	$104.11	$104.10	$104.10
Purchase #5	$80.99	13.275%	$91.7414	$91.74	$91.75	$91.70
Purchase #6	$59.51	3.750%	$61.7416	$61.74	$61.75	$61.70
Purchase #7	$98.27	11.644%	$109.7126	$109.71	$109.70	$109.70
7 purchase totals =	$842.13		$892.6045	$892.59	$892.60	$892.50