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	$112.67	9.285%	$123.1314	$123.13	$123.15	$123.10
Purchase #2	$248.49	9.181%	$271.3039	$271.30	$271.30	$271.30
Purchase #3	$141.88	5.812%	$150.1261	$150.13	$150.15	$150.10
Purchase #4	$194.31	9.468%	$212.7073	$212.71	$212.70	$212.70
Purchase #5	$40.56	6.250%	$43.095	$43.10	$43.10	$43.10
Purchase #6	$226.30	12.455%	$254.4857	$254.49	$254.50	$254.50
Purchase #7	$88.34	4.414%	$92.2393	$92.24	$92.25	$92.20
7 purchase totals =	$1,052.55		$1,147.0887	$1,147.10	$1,147.15	$1,147.00