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	$245.64	13.103%	$277.8262	$277.83	$277.85	$277.80
Purchase #2	$229.46	11.261%	$255.2995	$255.30	$255.30	$255.30
Purchase #3	$140.87	4.265%	$146.8781	$146.88	$146.90	$146.90
Purchase #4	$77.89	4.830%	$81.6521	$81.65	$81.65	$81.70
Purchase #5	$36.47	11.571%	$40.6899	$40.69	$40.70	$40.70
Purchase #6	$183.47	9.436%	$200.7822	$200.78	$200.80	$200.80
Purchase #7	$81.88	9.586%	$89.729	$89.73	$89.75	$89.70
7 purchase totals =	$995.68		$1,092.8570	$1,092.86	$1,092.95	$1,092.90