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	$33.73	8.179%	$36.4888	$36.49	$36.50	$36.50
Purchase #2	$151.55	4.625%	$158.5592	$158.56	$158.55	$158.60
Purchase #3	$132.70	4.353%	$138.4764	$138.48	$138.50	$138.50
Purchase #4	$145.46	8.740%	$158.1732	$158.17	$158.15	$158.20
Purchase #5	$106.76	4.692%	$111.7692	$111.77	$111.75	$111.80
Purchase #6	$170.49	11.205%	$189.5934	$189.59	$189.60	$189.60
Purchase #7	$216.34	4.712%	$226.5339	$226.53	$226.55	$226.50
7 purchase totals =	$957.03		$1,019.5941	$1,019.59	$1,019.60	$1,019.70