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	$105.66	5.210%	$111.1649	$111.16	$111.15	$111.20
Purchase #2	$232.33	7.146%	$248.9323	$248.93	$248.95	$248.90
Purchase #3	$56.61	4.687%	$59.2633	$59.26	$59.25	$59.30
Purchase #4	$90.41	10.380%	$99.7946	$99.79	$99.80	$99.80
Purchase #5	$221.75	9.190%	$242.1288	$242.13	$242.15	$242.10
Purchase #6	$57.55	6.856%	$61.4956	$61.50	$61.50	$61.50
Purchase #7	$49.80	5.166%	$52.3727	$52.37	$52.35	$52.40
7 purchase totals =	$814.11		$875.1522	$875.14	$875.15	$875.20