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	$138.63	4.858%	$145.3646	$145.36	$145.35	$145.40
Purchase #2	$163.58	12.626%	$184.2336	$184.23	$184.25	$184.20
Purchase #3	$66.42	9.180%	$72.5174	$72.52	$72.50	$72.50
Purchase #4	$186.78	13.165%	$211.3696	$211.37	$211.35	$211.40
Purchase #5	$56.29	9.355%	$61.5559	$61.56	$61.55	$61.60
Purchase #6	$125.91	4.739%	$131.8769	$131.88	$131.90	$131.90
Purchase #7	$245.76	13.441%	$278.7926	$278.79	$278.80	$278.80
7 purchase totals =	$983.37		$1,085.7106	$1,085.71	$1,085.70	$1,085.80