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	$152.28	13.183%	$172.3551	$172.36	$172.35	$172.40
Purchase #2	$85.96	7.719%	$92.5953	$92.60	$92.60	$92.60
Purchase #3	$223.85	9.400%	$244.8919	$244.89	$244.90	$244.90
Purchase #4	$230.56	12.290%	$258.8958	$258.90	$258.90	$258.90
Purchase #5	$206.69	10.808%	$229.0291	$229.03	$229.05	$229.00
Purchase #6	$13.35	8.755%	$14.5188	$14.52	$14.50	$14.50
Purchase #7	$135.60	3.615%	$140.5019	$140.50	$140.50	$140.50
7 purchase totals =	$1,048.29		$1,152.7879	$1,152.80	$1,152.80	$1,152.80