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	$224.69	8.743%	$244.3346	$244.33	$244.35	$244.30
Purchase #2	$249.82	12.682%	$281.5022	$281.50	$281.50	$281.50
Purchase #3	$197.25	12.560%	$222.0246	$222.02	$222.00	$222.00
Purchase #4	$77.95	7.147%	$83.5211	$83.52	$83.50	$83.50
Purchase #5	$75.44	13.179%	$85.3822	$85.38	$85.40	$85.40
Purchase #6	$109.99	6.119%	$116.7203	$116.72	$116.70	$116.70
Purchase #7	$59.87	9.764%	$65.7157	$65.72	$65.70	$65.70
7 purchase totals =	$995.01		$1,099.2007	$1,099.19	$1,099.15	$1,099.10