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	$40.90	11.864%	$45.7524	$45.75	$45.75	$45.80
Purchase #2	$125.51	6.540%	$133.7184	$133.72	$133.70	$133.70
Purchase #3	$187.33	4.741%	$196.2113	$196.21	$196.20	$196.20
Purchase #4	$60.86	4.366%	$63.5171	$63.52	$63.50	$63.50
Purchase #5	$212.45	6.747%	$226.784	$226.78	$226.80	$226.80
Purchase #6	$194.39	12.217%	$218.1386	$218.14	$218.15	$218.10
Purchase #7	$185.50	4.272%	$193.4246	$193.42	$193.40	$193.40
7 purchase totals =	$1,006.94		$1,077.5464	$1,077.54	$1,077.50	$1,077.50