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	$58.27	6.526%	$62.0727	$62.07	$62.05	$62.10
Purchase #2	$111.44	11.822%	$124.6144	$124.61	$124.60	$124.60
Purchase #3	$49.41	5.276%	$52.0169	$52.02	$52.00	$52.00
Purchase #4	$85.40	6.103%	$90.612	$90.61	$90.60	$90.60
Purchase #5	$181.89	9.841%	$199.7898	$199.79	$199.80	$199.80
Purchase #6	$30.98	3.132%	$31.9503	$31.95	$31.95	$32.00
Purchase #7	$87.43	7.156%	$93.6865	$93.69	$93.70	$93.70
7 purchase totals =	$604.82		$654.7426	$654.74	$654.70	$654.80