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	$119.87	13.636%	$136.2155	$136.22	$136.20	$136.20
Purchase #2	$40.90	13.603%	$46.4636	$46.46	$46.45	$46.50
Purchase #3	$56.28	5.487%	$59.3681	$59.37	$59.35	$59.40
Purchase #4	$103.62	5.359%	$109.173	$109.17	$109.15	$109.20
Purchase #5	$229.36	11.752%	$256.3144	$256.31	$256.30	$256.30
Purchase #6	$228.31	7.144%	$244.6205	$244.62	$244.60	$244.60
Purchase #7	$119.57	13.278%	$135.4465	$135.45	$135.45	$135.40
7 purchase totals =	$897.91		$987.6016	$987.60	$987.50	$987.60