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	$224.46	13.352%	$254.4299	$254.43	$254.45	$254.40
Purchase #2	$178.75	5.205%	$188.0539	$188.05	$188.05	$188.10
Purchase #3	$169.56	9.346%	$185.4071	$185.41	$185.40	$185.40
Purchase #4	$188.36	9.485%	$206.2259	$206.23	$206.25	$206.20
Purchase #5	$233.27	4.180%	$243.0207	$243.02	$243.00	$243.00
Purchase #6	$42.53	4.836%	$44.5868	$44.59	$44.60	$44.60
Purchase #7	$91.95	12.188%	$103.1569	$103.16	$103.15	$103.20
7 purchase totals =	$1,128.88		$1,224.8812	$1,224.89	$1,224.90	$1,224.90