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	$210.58	13.261%	$238.505	$238.51	$238.50	$238.50
Purchase #2	$167.61	10.548%	$185.2895	$185.29	$185.30	$185.30
Purchase #3	$73.96	11.344%	$82.35	$82.35	$82.35	$82.40
Purchase #4	$28.99	10.616%	$32.0676	$32.07	$32.05	$32.10
Purchase #5	$188.79	11.231%	$209.993	$209.99	$210.00	$210.00
Purchase #6	$89.41	3.200%	$92.2711	$92.27	$92.25	$92.30
Purchase #7	$224.47	8.415%	$243.3592	$243.36	$243.35	$243.40
7 purchase totals =	$983.81		$1,083.8354	$1,083.84	$1,083.80	$1,084.00