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	$247.88	6.339%	$263.5931	$263.59	$263.60	$263.60
Purchase #2	$68.65	6.634%	$73.2042	$73.20	$73.20	$73.20
Purchase #3	$69.96	12.169%	$78.4734	$78.47	$78.45	$78.50
Purchase #4	$12.60	4.570%	$13.1758	$13.18	$13.20	$13.20
Purchase #5	$167.96	3.660%	$174.1073	$174.11	$174.10	$174.10
Purchase #6	$141.73	6.748%	$151.2939	$151.29	$151.30	$151.30
Purchase #7	$119.34	3.673%	$123.7234	$123.72	$123.70	$123.70
7 purchase totals =	$828.12		$877.5711	$877.56	$877.55	$877.60