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	$162.61	10.389%	$179.5036	$179.50	$179.50	$179.50
Purchase #2	$16.48	9.740%	$18.0852	$18.09	$18.10	$18.10
Purchase #3	$28.43	12.432%	$31.9644	$31.96	$31.95	$32.00
Purchase #4	$191.70	10.680%	$212.1736	$212.17	$212.15	$212.20
Purchase #5	$172.54	7.676%	$185.7842	$185.78	$185.80	$185.80
Purchase #6	$37.79	6.422%	$40.2169	$40.22	$40.20	$40.20
Purchase #7	$116.80	9.415%	$127.7967	$127.80	$127.80	$127.80
7 purchase totals =	$726.35		$795.5246	$795.52	$795.50	$795.60