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	$88.56	8.349%	$95.9539	$95.95	$95.95	$96.00
Purchase #2	$103.91	10.839%	$115.1728	$115.17	$115.15	$115.20
Purchase #3	$41.39	10.242%	$45.6292	$45.63	$45.65	$45.60
Purchase #4	$222.62	4.146%	$231.8498	$231.85	$231.85	$231.80
Purchase #5	$37.92	5.741%	$40.097	$40.10	$40.10	$40.10
Purchase #6	$89.83	6.414%	$95.5917	$95.59	$95.60	$95.60
Purchase #7	$243.42	5.412%	$256.5939	$256.59	$256.60	$256.60
7 purchase totals =	$827.65		$880.8883	$880.88	$880.90	$880.90