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	$163.95	10.525%	$181.2057	$181.21	$181.20	$181.20
Purchase #2	$51.46	11.547%	$57.4021	$57.40	$57.40	$57.40
Purchase #3	$88.57	3.305%	$91.4972	$91.50	$91.50	$91.50
Purchase #4	$57.51	9.243%	$62.8256	$62.83	$62.85	$62.80
Purchase #5	$72.98	13.282%	$82.6732	$82.67	$82.65	$82.70
Purchase #6	$174.72	8.693%	$189.9084	$189.91	$189.90	$189.90
Purchase #7	$39.29	9.122%	$42.874	$42.87	$42.85	$42.90
7 purchase totals =	$648.48		$708.3862	$708.39	$708.35	$708.40