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	$188.72	3.136%	$194.6383	$194.64	$194.65	$194.60
Purchase #2	$107.72	3.821%	$111.836	$111.84	$111.85	$111.80
Purchase #3	$197.34	8.676%	$214.4612	$214.46	$214.45	$214.50
Purchase #4	$175.86	9.130%	$191.916	$191.92	$191.90	$191.90
Purchase #5	$68.48	12.642%	$77.1372	$77.14	$77.15	$77.10
Purchase #6	$250.66	4.872%	$262.8722	$262.87	$262.85	$262.90
Purchase #7	$109.80	6.489%	$116.9249	$116.92	$116.90	$116.90
7 purchase totals =	$1,098.58		$1,169.7858	$1,169.79	$1,169.75	$1,169.70