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	$38.51	8.323%	$41.7152	$41.72	$41.70	$41.70
Purchase #2	$216.27	13.727%	$245.9574	$245.96	$245.95	$246.00
Purchase #3	$25.98	11.380%	$28.9365	$28.94	$28.95	$28.90
Purchase #4	$82.29	9.845%	$90.3915	$90.39	$90.40	$90.40
Purchase #5	$11.27	6.696%	$12.0246	$12.02	$12.00	$12.00
Purchase #6	$70.81	3.233%	$73.0993	$73.10	$73.10	$73.10
Purchase #7	$118.38	11.375%	$131.8457	$131.85	$131.85	$131.80
7 purchase totals =	$563.51		$623.9702	$623.98	$623.95	$623.90