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	$87.69	10.740%	$97.1079	$97.11	$97.10	$97.10
Purchase #2	$98.77	6.182%	$104.876	$104.88	$104.90	$104.90
Purchase #3	$248.29	13.460%	$281.7098	$281.71	$281.70	$281.70
Purchase #4	$213.60	7.282%	$229.1544	$229.15	$229.15	$229.20
Purchase #5	$69.58	3.315%	$71.8866	$71.89	$71.90	$71.90
Purchase #6	$35.62	6.400%	$37.8997	$37.90	$37.90	$37.90
Purchase #7	$234.90	12.305%	$263.8044	$263.80	$263.80	$263.80
7 purchase totals =	$988.45		$1,086.4388	$1,086.44	$1,086.45	$1,086.50