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	$223.70	13.811%	$254.5952	$254.60	$254.60	$254.60
Purchase #2	$151.52	10.562%	$167.5235	$167.52	$167.50	$167.50
Purchase #3	$106.71	4.367%	$111.37	$111.37	$111.35	$111.40
Purchase #4	$180.51	4.859%	$189.281	$189.28	$189.30	$189.30
Purchase #5	$81.95	11.866%	$91.6742	$91.67	$91.65	$91.70
Purchase #6	$41.89	6.396%	$44.5693	$44.57	$44.55	$44.60
Purchase #7	$222.70	7.522%	$239.4515	$239.45	$239.45	$239.50
7 purchase totals =	$1,008.98		$1,098.4647	$1,098.46	$1,098.40	$1,098.60