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	$213.60	4.823%	$223.9019	$223.90	$223.90	$223.90
Purchase #2	$83.68	6.826%	$89.392	$89.39	$89.40	$89.40
Purchase #3	$41.30	5.701%	$43.6545	$43.65	$43.65	$43.70
Purchase #4	$54.41	4.817%	$57.0309	$57.03	$57.05	$57.00
Purchase #5	$225.35	13.332%	$255.3937	$255.39	$255.40	$255.40
Purchase #6	$156.62	6.285%	$166.4636	$166.46	$166.45	$166.50
Purchase #7	$237.98	8.476%	$258.1512	$258.15	$258.15	$258.20
7 purchase totals =	$1,012.94		$1,093.9878	$1,093.97	$1,094.00	$1,094.10