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	$226.42	4.619%	$236.8783	$236.88	$236.90	$236.90
Purchase #2	$45.79	5.578%	$48.3442	$48.34	$48.35	$48.30
Purchase #3	$211.58	5.660%	$223.5554	$223.56	$223.55	$223.60
Purchase #4	$166.89	11.355%	$185.8404	$185.84	$185.85	$185.80
Purchase #5	$28.98	6.182%	$30.7715	$30.77	$30.75	$30.80
Purchase #6	$199.30	10.830%	$220.8842	$220.88	$220.90	$220.90
Purchase #7	$228.71	11.117%	$254.1357	$254.14	$254.15	$254.10
7 purchase totals =	$1,107.67		$1,200.4097	$1,200.41	$1,200.45	$1,200.40