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	$48.75	12.208%	$54.7014	$54.70	$54.70	$54.70
Purchase #2	$194.70	8.508%	$211.2651	$211.27	$211.25	$211.30
Purchase #3	$58.41	13.104%	$66.064	$66.06	$66.05	$66.10
Purchase #4	$127.50	3.222%	$131.6081	$131.61	$131.60	$131.60
Purchase #5	$222.94	7.717%	$240.1443	$240.14	$240.15	$240.10
Purchase #6	$78.33	3.356%	$80.9588	$80.96	$80.95	$81.00
Purchase #7	$164.45	8.739%	$178.8213	$178.82	$178.80	$178.80
7 purchase totals =	$895.08		$963.5630	$963.56	$963.50	$963.60