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	$14.42	3.156%	$14.8751	$14.88	$14.90	$14.90
Purchase #2	$235.92	11.404%	$262.8243	$262.82	$262.80	$262.80
Purchase #3	$244.43	6.822%	$261.105	$261.11	$261.10	$261.10
Purchase #4	$33.62	6.229%	$35.7142	$35.71	$35.70	$35.70
Purchase #5	$121.25	8.268%	$131.275	$131.28	$131.30	$131.30
Purchase #6	$166.34	13.809%	$189.3099	$189.31	$189.30	$189.30
Purchase #7	$236.59	6.150%	$251.1403	$251.14	$251.15	$251.10
7 purchase totals =	$1,052.57		$1,146.2438	$1,146.25	$1,146.25	$1,146.20