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	$218.34	13.543%	$247.9098	$247.91	$247.90	$247.90
Purchase #2	$205.82	12.481%	$231.5084	$231.51	$231.50	$231.50
Purchase #3	$238.39	11.117%	$264.8918	$264.89	$264.90	$264.90
Purchase #4	$179.55	6.624%	$191.4434	$191.44	$191.45	$191.40
Purchase #5	$41.65	11.722%	$46.5322	$46.53	$46.55	$46.50
Purchase #6	$42.46	12.446%	$47.7446	$47.74	$47.75	$47.70
Purchase #7	$53.65	5.591%	$56.6496	$56.65	$56.65	$56.60
7 purchase totals =	$979.86		$1,086.6798	$1,086.67	$1,086.70	$1,086.50