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	$92.74	4.539%	$96.9495	$96.95	$96.95	$96.90
Purchase #2	$95.67	3.663%	$99.1744	$99.17	$99.15	$99.20
Purchase #3	$243.88	11.753%	$272.5432	$272.54	$272.55	$272.50
Purchase #4	$185.71	4.673%	$194.3882	$194.39	$194.40	$194.40
Purchase #5	$199.72	5.568%	$210.8404	$210.84	$210.85	$210.80
Purchase #6	$200.41	10.359%	$221.1705	$221.17	$221.15	$221.20
Purchase #7	$90.92	4.528%	$95.0369	$95.04	$95.05	$95.00
7 purchase totals =	$1,109.05		$1,190.1031	$1,190.10	$1,190.10	$1,190.00