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	$241.52	5.696%	$255.277	$255.28	$255.30	$255.30
Purchase #2	$134.26	13.112%	$151.8642	$151.86	$151.85	$151.90
Purchase #3	$116.71	11.571%	$130.2145	$130.21	$130.20	$130.20
Purchase #4	$229.55	7.732%	$247.2988	$247.30	$247.30	$247.30
Purchase #5	$143.60	9.206%	$156.8198	$156.82	$156.80	$156.80
Purchase #6	$178.33	9.852%	$195.8991	$195.90	$195.90	$195.90
Purchase #7	$55.41	12.120%	$62.1257	$62.13	$62.15	$62.10
7 purchase totals =	$1,099.38		$1,199.4991	$1,199.50	$1,199.50	$1,199.50