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	$196.34	13.366%	$222.5828	$222.58	$222.60	$222.60
Purchase #2	$205.90	13.729%	$234.168	$234.17	$234.15	$234.20
Purchase #3	$12.44	11.776%	$13.9049	$13.90	$13.90	$13.90
Purchase #4	$64.46	3.512%	$66.7238	$66.72	$66.70	$66.70
Purchase #5	$141.84	7.435%	$152.3858	$152.39	$152.40	$152.40
Purchase #6	$154.25	7.644%	$166.0409	$166.04	$166.05	$166.00
Purchase #7	$152.99	4.610%	$160.0428	$160.04	$160.05	$160.00
7 purchase totals =	$928.22		$1,015.8490	$1,015.84	$1,015.85	$1,015.80