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	$16.72	13.726%	$19.015	$19.02	$19.00	$19.00
Purchase #2	$189.94	13.791%	$216.1346	$216.13	$216.15	$216.10
Purchase #3	$81.67	11.222%	$90.835	$90.84	$90.85	$90.80
Purchase #4	$104.50	4.531%	$109.2349	$109.23	$109.25	$109.20
Purchase #5	$114.76	13.475%	$130.2239	$130.22	$130.20	$130.20
Purchase #6	$174.73	9.269%	$190.9257	$190.93	$190.95	$190.90
Purchase #7	$190.98	3.240%	$197.1678	$197.17	$197.15	$197.20
7 purchase totals =	$873.30		$953.5369	$953.54	$953.55	$953.40