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	$99.50	13.174%	$112.6081	$112.61	$112.60	$112.60
Purchase #2	$124.76	7.819%	$134.515	$134.52	$134.50	$134.50
Purchase #3	$238.50	10.364%	$263.2181	$263.22	$263.20	$263.20
Purchase #4	$244.83	3.776%	$254.0748	$254.07	$254.05	$254.10
Purchase #5	$143.35	3.789%	$148.7815	$148.78	$148.80	$148.80
Purchase #6	$41.81	12.183%	$46.9037	$46.90	$46.90	$46.90
Purchase #7	$236.82	13.642%	$269.127	$269.13	$269.15	$269.10
7 purchase totals =	$1,129.57		$1,229.2282	$1,229.23	$1,229.20	$1,229.20