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	$237.54	11.501%	$264.8595	$264.86	$264.85	$264.90
Purchase #2	$165.83	11.686%	$185.2089	$185.21	$185.20	$185.20
Purchase #3	$230.27	5.784%	$243.5888	$243.59	$243.60	$243.60
Purchase #4	$176.89	7.177%	$189.5854	$189.59	$189.60	$189.60
Purchase #5	$35.39	12.518%	$39.8201	$39.82	$39.80	$39.80
Purchase #6	$8.96	9.724%	$9.8313	$9.83	$9.85	$9.80
Purchase #7	$169.35	13.349%	$191.9565	$191.96	$191.95	$192.00
7 purchase totals =	$1,024.23		$1,124.8505	$1,124.86	$1,124.85	$1,124.90