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	$213.27	13.505%	$242.0721	$242.07	$242.05	$242.10
Purchase #2	$224.70	10.108%	$247.4127	$247.41	$247.40	$247.40
Purchase #3	$161.86	12.289%	$181.751	$181.75	$181.75	$181.80
Purchase #4	$96.83	11.512%	$107.9771	$107.98	$108.00	$108.00
Purchase #5	$48.55	12.625%	$54.6794	$54.68	$54.70	$54.70
Purchase #6	$37.80	11.714%	$42.2279	$42.23	$42.25	$42.20
Purchase #7	$186.51	5.298%	$196.3913	$196.39	$196.40	$196.40
7 purchase totals =	$969.52		$1,072.5115	$1,072.51	$1,072.55	$1,072.60