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	$188.28	9.131%	$205.4718	$205.47	$205.45	$205.50
Purchase #2	$247.59	11.453%	$275.9465	$275.95	$275.95	$275.90
Purchase #3	$74.36	11.264%	$82.7359	$82.74	$82.75	$82.70
Purchase #4	$147.72	4.857%	$154.8948	$154.89	$154.90	$154.90
Purchase #5	$107.90	11.853%	$120.6894	$120.69	$120.70	$120.70
Purchase #6	$42.72	12.103%	$47.8904	$47.89	$47.90	$47.90
Purchase #7	$236.64	5.416%	$249.4564	$249.46	$249.45	$249.50
7 purchase totals =	$1,045.21		$1,137.0852	$1,137.09	$1,137.10	$1,137.10