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	$101.58	10.358%	$112.1017	$112.10	$112.10	$112.10
Purchase #2	$99.40	7.847%	$107.1999	$107.20	$107.20	$107.20
Purchase #3	$40.35	3.477%	$41.753	$41.75	$41.75	$41.80
Purchase #4	$133.59	13.391%	$151.479	$151.48	$151.50	$151.50
Purchase #5	$84.73	13.433%	$96.1118	$96.11	$96.10	$96.10
Purchase #6	$42.31	6.611%	$45.1071	$45.11	$45.10	$45.10
Purchase #7	$187.31	11.805%	$209.4219	$209.42	$209.40	$209.40
7 purchase totals =	$689.27		$763.1744	$763.17	$763.15	$763.20