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	$156.56	7.120%	$167.7071	$167.71	$167.70	$167.70
Purchase #2	$151.66	4.536%	$158.5393	$158.54	$158.55	$158.50
Purchase #3	$119.56	12.779%	$134.8386	$134.84	$134.85	$134.80
Purchase #4	$229.71	3.840%	$238.5309	$238.53	$238.55	$238.50
Purchase #5	$165.46	13.448%	$187.7111	$187.71	$187.70	$187.70
Purchase #6	$152.71	3.805%	$158.5206	$158.52	$158.50	$158.50
Purchase #7	$90.59	11.617%	$101.1138	$101.11	$101.10	$101.10
7 purchase totals =	$1,066.25		$1,146.9614	$1,146.96	$1,146.95	$1,146.80