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	$148.35	4.693%	$155.3121	$155.31	$155.30	$155.30
Purchase #2	$69.46	7.594%	$74.7348	$74.73	$74.75	$74.70
Purchase #3	$146.61	6.719%	$156.4607	$156.46	$156.45	$156.50
Purchase #4	$180.41	4.383%	$188.3174	$188.32	$188.30	$188.30
Purchase #5	$43.65	3.300%	$45.0905	$45.09	$45.10	$45.10
Purchase #6	$227.86	11.624%	$254.3464	$254.35	$254.35	$254.30
Purchase #7	$161.77	12.171%	$181.459	$181.46	$181.45	$181.50
7 purchase totals =	$978.11		$1,055.7209	$1,055.72	$1,055.70	$1,055.70