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	$181.46	8.198%	$196.3361	$196.34	$196.35	$196.30
Purchase #2	$48.64	10.583%	$53.7876	$53.79	$53.80	$53.80
Purchase #3	$223.34	6.803%	$238.5338	$238.53	$238.55	$238.50
Purchase #4	$81.90	9.196%	$89.4315	$89.43	$89.45	$89.40
Purchase #5	$229.89	7.775%	$247.7639	$247.76	$247.75	$247.80
Purchase #6	$71.50	7.247%	$76.6816	$76.68	$76.70	$76.70
Purchase #7	$106.36	13.336%	$120.5442	$120.54	$120.55	$120.50
7 purchase totals =	$943.09		$1,023.0787	$1,023.07	$1,023.15	$1,023.00