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	$218.55	8.134%	$236.3269	$236.33	$236.35	$236.30
Purchase #2	$78.72	10.138%	$86.7006	$86.70	$86.70	$86.70
Purchase #3	$141.72	7.190%	$151.9097	$151.91	$151.90	$151.90
Purchase #4	$128.50	13.267%	$145.5481	$145.55	$145.55	$145.50
Purchase #5	$168.42	7.378%	$180.846	$180.85	$180.85	$180.80
Purchase #6	$174.76	4.238%	$182.1663	$182.17	$182.15	$182.20
Purchase #7	$31.81	5.115%	$33.4371	$33.44	$33.45	$33.40
7 purchase totals =	$942.48		$1,016.9347	$1,016.95	$1,016.95	$1,016.80