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	$69.45	3.623%	$71.9662	$71.97	$71.95	$72.00
Purchase #2	$31.65	8.134%	$34.2244	$34.22	$34.20	$34.20
Purchase #3	$39.47	6.123%	$41.8867	$41.89	$41.90	$41.90
Purchase #4	$204.86	7.608%	$220.4457	$220.45	$220.45	$220.40
Purchase #5	$245.50	12.143%	$275.3111	$275.31	$275.30	$275.30
Purchase #6	$224.69	11.123%	$249.6823	$249.68	$249.70	$249.70
Purchase #7	$131.95	12.580%	$148.5493	$148.55	$148.55	$148.50
7 purchase totals =	$947.57		$1,042.0657	$1,042.07	$1,042.05	$1,042.00