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	$131.60	8.239%	$142.4425	$142.44	$142.45	$142.40
Purchase #2	$116.83	9.624%	$128.0737	$128.07	$128.05	$128.10
Purchase #3	$22.98	7.860%	$24.7862	$24.79	$24.80	$24.80
Purchase #4	$90.25	10.683%	$99.8914	$99.89	$99.90	$99.90
Purchase #5	$179.74	4.288%	$187.4473	$187.45	$187.45	$187.40
Purchase #6	$122.72	4.869%	$128.6952	$128.70	$128.70	$128.70
Purchase #7	$159.65	9.502%	$174.8199	$174.82	$174.80	$174.80
7 purchase totals =	$823.77		$886.1562	$886.16	$886.15	$886.10