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	$169.90	11.329%	$189.148	$189.15	$189.15	$189.10
Purchase #2	$128.77	10.480%	$142.2651	$142.27	$142.25	$142.30
Purchase #3	$106.96	4.627%	$111.909	$111.91	$111.90	$111.90
Purchase #4	$58.52	12.465%	$65.8145	$65.81	$65.80	$65.80
Purchase #5	$87.87	3.240%	$90.717	$90.72	$90.70	$90.70
Purchase #6	$245.34	12.245%	$275.3819	$275.38	$275.40	$275.40
Purchase #7	$135.52	3.123%	$139.7523	$139.75	$139.75	$139.80
7 purchase totals =	$932.88		$1,014.9878	$1,014.99	$1,014.95	$1,015.00