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	$203.41	5.846%	$215.3013	$215.30	$215.30	$215.30
Purchase #2	$184.38	13.106%	$208.5448	$208.54	$208.55	$208.50
Purchase #3	$137.69	3.453%	$142.4444	$142.44	$142.45	$142.40
Purchase #4	$24.85	10.598%	$27.4836	$27.48	$27.50	$27.50
Purchase #5	$129.27	6.681%	$137.9065	$137.91	$137.90	$137.90
Purchase #6	$121.31	7.222%	$130.071	$130.07	$130.05	$130.10
Purchase #7	$160.38	5.265%	$168.824	$168.82	$168.80	$168.80
7 purchase totals =	$961.29		$1,030.5756	$1,030.56	$1,030.55	$1,030.50