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	$134.98	13.302%	$152.935	$152.94	$152.95	$152.90
Purchase #2	$227.86	9.791%	$250.1698	$250.17	$250.15	$250.20
Purchase #3	$65.69	13.133%	$74.3171	$74.32	$74.30	$74.30
Purchase #4	$112.62	3.404%	$116.4536	$116.45	$116.45	$116.50
Purchase #5	$222.25	11.766%	$248.3999	$248.40	$248.40	$248.40
Purchase #6	$249.80	6.166%	$265.2027	$265.20	$265.20	$265.20
Purchase #7	$82.95	8.603%	$90.0862	$90.09	$90.10	$90.10
7 purchase totals =	$1,096.15		$1,197.5643	$1,197.57	$1,197.55	$1,197.60