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	$68.46	4.267%	$71.3812	$71.38	$71.40	$71.40
Purchase #2	$20.28	10.392%	$22.3875	$22.39	$22.40	$22.40
Purchase #3	$196.31	13.336%	$222.4899	$222.49	$222.50	$222.50
Purchase #4	$48.77	5.453%	$51.4294	$51.43	$51.45	$51.40
Purchase #5	$48.61	12.119%	$54.501	$54.50	$54.50	$54.50
Purchase #6	$243.61	8.336%	$263.9173	$263.92	$263.90	$263.90
Purchase #7	$246.73	10.520%	$272.686	$272.69	$272.70	$272.70
7 purchase totals =	$872.77		$958.7923	$958.80	$958.85	$958.80