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	$113.81	12.414%	$127.9384	$127.94	$127.95	$127.90
Purchase #2	$33.99	4.764%	$35.6093	$35.61	$35.60	$35.60
Purchase #3	$216.25	13.657%	$245.7833	$245.78	$245.80	$245.80
Purchase #4	$5.28	3.319%	$5.4552	$5.46	$5.45	$5.50
Purchase #5	$162.28	10.777%	$179.7689	$179.77	$179.75	$179.80
Purchase #6	$55.32	9.336%	$60.4847	$60.48	$60.50	$60.50
Purchase #7	$151.56	4.430%	$158.2741	$158.27	$158.25	$158.30
7 purchase totals =	$738.49		$813.3139	$813.31	$813.30	$813.40