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	$168.52	10.173%	$185.6635	$185.66	$185.65	$185.70
Purchase #2	$204.69	9.687%	$224.5183	$224.52	$224.50	$224.50
Purchase #3	$222.53	8.569%	$241.5986	$241.60	$241.60	$241.60
Purchase #4	$226.82	9.215%	$247.7215	$247.72	$247.70	$247.70
Purchase #5	$186.36	5.343%	$196.3172	$196.32	$196.30	$196.30
Purchase #6	$75.33	13.308%	$85.3549	$85.35	$85.35	$85.40
Purchase #7	$193.96	3.515%	$200.7777	$200.78	$200.80	$200.80
7 purchase totals =	$1,278.21		$1,381.9517	$1,381.95	$1,381.90	$1,382.00