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	$173.35	13.431%	$196.6326	$196.63	$196.65	$196.60
Purchase #2	$67.66	9.578%	$74.1405	$74.14	$74.15	$74.10
Purchase #3	$11.90	3.466%	$12.3125	$12.31	$12.30	$12.30
Purchase #4	$82.95	3.105%	$85.5256	$85.53	$85.55	$85.50
Purchase #5	$182.44	5.118%	$191.7773	$191.78	$191.80	$191.80
Purchase #6	$54.93	5.511%	$57.9572	$57.96	$57.95	$58.00
Purchase #7	$242.61	10.640%	$268.4237	$268.42	$268.40	$268.40
7 purchase totals =	$815.84		$886.7694	$886.77	$886.80	$886.70