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	$139.26	9.863%	$152.9952	$153.00	$153.00	$153.00
Purchase #2	$55.82	10.230%	$61.5304	$61.53	$61.55	$61.50
Purchase #3	$183.43	4.350%	$191.4092	$191.41	$191.40	$191.40
Purchase #4	$85.51	6.301%	$90.898	$90.90	$90.90	$90.90
Purchase #5	$177.26	8.687%	$192.6586	$192.66	$192.65	$192.70
Purchase #6	$170.50	13.102%	$192.8389	$192.84	$192.85	$192.80
Purchase #7	$39.82	3.323%	$41.1432	$41.14	$41.15	$41.10
7 purchase totals =	$851.60		$923.4735	$923.48	$923.50	$923.40