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	$13.71	3.874%	$14.2411	$14.24	$14.25	$14.20
Purchase #2	$244.72	12.558%	$275.4519	$275.45	$275.45	$275.50
Purchase #3	$188.82	5.562%	$199.3222	$199.32	$199.30	$199.30
Purchase #4	$153.60	9.540%	$168.2534	$168.25	$168.25	$168.30
Purchase #5	$160.45	5.460%	$169.2106	$169.21	$169.20	$169.20
Purchase #6	$191.66	9.115%	$209.1298	$209.13	$209.15	$209.10
Purchase #7	$35.79	11.609%	$39.9449	$39.94	$39.95	$39.90
7 purchase totals =	$988.75		$1,075.5539	$1,075.54	$1,075.55	$1,075.50