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	$67.66	5.801%	$71.585	$71.59	$71.60	$71.60
Purchase #2	$229.46	6.553%	$244.4965	$244.50	$244.50	$244.50
Purchase #3	$141.43	6.690%	$150.8917	$150.89	$150.90	$150.90
Purchase #4	$188.25	9.727%	$206.5611	$206.56	$206.55	$206.60
Purchase #5	$146.73	9.501%	$160.6708	$160.67	$160.65	$160.70
Purchase #6	$167.65	8.190%	$181.3805	$181.38	$181.40	$181.40
Purchase #7	$237.41	13.224%	$268.8051	$268.81	$268.80	$268.80
7 purchase totals =	$1,178.59		$1,284.3907	$1,284.40	$1,284.40	$1,284.50