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	$80.26	11.687%	$89.64	$89.64	$89.65	$89.60
Purchase #2	$234.30	10.595%	$259.1241	$259.12	$259.10	$259.10
Purchase #3	$53.62	8.261%	$58.0495	$58.05	$58.05	$58.00
Purchase #4	$78.67	4.826%	$82.4666	$82.47	$82.45	$82.50
Purchase #5	$243.90	4.502%	$254.8804	$254.88	$254.90	$254.90
Purchase #6	$233.66	4.533%	$244.2518	$244.25	$244.25	$244.30
Purchase #7	$200.93	10.572%	$222.1723	$222.17	$222.15	$222.20
7 purchase totals =	$1,125.34		$1,210.5847	$1,210.58	$1,210.55	$1,210.60