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	$226.72	10.591%	$250.7319	$250.73	$250.75	$250.70
Purchase #2	$102.78	6.737%	$109.7043	$109.70	$109.70	$109.70
Purchase #3	$55.72	6.455%	$59.3167	$59.32	$59.30	$59.30
Purchase #4	$185.60	8.261%	$200.9324	$200.93	$200.95	$200.90
Purchase #5	$23.28	13.829%	$26.4994	$26.50	$26.50	$26.50
Purchase #6	$50.25	11.765%	$56.1619	$56.16	$56.15	$56.20
Purchase #7	$154.90	10.329%	$170.8996	$170.90	$170.90	$170.90
7 purchase totals =	$799.25		$874.2462	$874.24	$874.25	$874.20