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	$41.42	11.666%	$46.2521	$46.25	$46.25	$46.30
Purchase #2	$236.36	7.822%	$254.8481	$254.85	$254.85	$254.80
Purchase #3	$115.36	10.791%	$127.8085	$127.81	$127.80	$127.80
Purchase #4	$84.48	13.108%	$95.5536	$95.55	$95.55	$95.60
Purchase #5	$213.82	4.488%	$223.4162	$223.42	$223.40	$223.40
Purchase #6	$153.31	4.253%	$159.8303	$159.83	$159.85	$159.80
Purchase #7	$59.48	4.681%	$62.2643	$62.26	$62.25	$62.30
7 purchase totals =	$904.23		$969.9731	$969.97	$969.95	$970.00