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	$97.32	6.317%	$103.4677	$103.47	$103.45	$103.50
Purchase #2	$69.58	11.300%	$77.4425	$77.44	$77.45	$77.40
Purchase #3	$146.94	5.870%	$155.5654	$155.57	$155.55	$155.60
Purchase #4	$239.97	3.608%	$248.6281	$248.63	$248.65	$248.60
Purchase #5	$118.42	12.575%	$133.3113	$133.31	$133.30	$133.30
Purchase #6	$205.32	8.489%	$222.7496	$222.75	$222.75	$222.70
Purchase #7	$139.90	9.290%	$152.8967	$152.90	$152.90	$152.90
7 purchase totals =	$1,017.45		$1,094.0613	$1,094.07	$1,094.05	$1,094.00