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	$125.55	4.205%	$130.8294	$130.83	$130.85	$130.80
Purchase #2	$97.91	12.205%	$109.8599	$109.86	$109.85	$109.90
Purchase #3	$44.37	8.206%	$48.011	$48.01	$48.00	$48.00
Purchase #4	$171.58	8.105%	$185.4866	$185.49	$185.50	$185.50
Purchase #5	$104.69	12.797%	$118.0872	$118.09	$118.10	$118.10
Purchase #6	$192.76	9.553%	$211.1744	$211.17	$211.15	$211.20
Purchase #7	$247.89	11.290%	$275.8768	$275.88	$275.90	$275.90
7 purchase totals =	$984.75		$1,079.3253	$1,079.33	$1,079.35	$1,079.40