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	$174.33	6.177%	$185.0984	$185.10	$185.10	$185.10
Purchase #2	$174.66	9.299%	$190.9016	$190.90	$190.90	$190.90
Purchase #3	$166.66	7.301%	$178.8278	$178.83	$178.85	$178.80
Purchase #4	$239.74	4.467%	$250.4492	$250.45	$250.45	$250.40
Purchase #5	$59.32	5.473%	$62.5666	$62.57	$62.55	$62.60
Purchase #6	$221.53	12.129%	$248.3994	$248.40	$248.40	$248.40
Purchase #7	$141.81	7.154%	$151.9551	$151.96	$151.95	$152.00
7 purchase totals =	$1,178.05		$1,268.1981	$1,268.21	$1,268.20	$1,268.20