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	$165.50	13.453%	$187.7647	$187.76	$187.75	$187.80
Purchase #2	$147.72	9.778%	$162.1641	$162.16	$162.15	$162.20
Purchase #3	$35.99	11.842%	$40.2519	$40.25	$40.25	$40.30
Purchase #4	$89.54	12.670%	$100.8847	$100.88	$100.90	$100.90
Purchase #5	$55.78	4.499%	$58.2895	$58.29	$58.30	$58.30
Purchase #6	$199.36	12.641%	$224.5611	$224.56	$224.55	$224.60
Purchase #7	$25.58	7.386%	$27.4693	$27.47	$27.45	$27.50
7 purchase totals =	$719.47		$801.3853	$801.37	$801.35	$801.60