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	$195.26	11.219%	$217.1662	$217.17	$217.15	$217.20
Purchase #2	$44.74	12.671%	$50.409	$50.41	$50.40	$50.40
Purchase #3	$142.80	6.166%	$151.605	$151.61	$151.60	$151.60
Purchase #4	$15.41	5.792%	$16.3025	$16.30	$16.30	$16.30
Purchase #5	$119.67	12.424%	$134.5378	$134.54	$134.55	$134.50
Purchase #6	$36.33	13.205%	$41.1274	$41.13	$41.15	$41.10
Purchase #7	$79.31	12.397%	$89.1421	$89.14	$89.15	$89.10
7 purchase totals =	$633.52		$700.2900	$700.30	$700.30	$700.20