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	$63.53	6.781%	$67.838	$67.84	$67.85	$67.80
Purchase #2	$246.75	6.573%	$262.9689	$262.97	$262.95	$263.00
Purchase #3	$37.59	3.548%	$38.9237	$38.92	$38.90	$38.90
Purchase #4	$61.89	3.762%	$64.2183	$64.22	$64.20	$64.20
Purchase #5	$232.96	5.410%	$245.5631	$245.56	$245.55	$245.60
Purchase #6	$229.38	10.563%	$253.6094	$253.61	$253.60	$253.60
Purchase #7	$119.56	9.836%	$131.3199	$131.32	$131.30	$131.30
7 purchase totals =	$991.66		$1,064.4413	$1,064.44	$1,064.35	$1,064.40