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	$155.40	4.589%	$162.5313	$162.53	$162.55	$162.50
Purchase #2	$142.59	4.221%	$148.6087	$148.61	$148.60	$148.60
Purchase #3	$244.56	10.650%	$270.6056	$270.61	$270.60	$270.60
Purchase #4	$174.54	5.851%	$184.7523	$184.75	$184.75	$184.80
Purchase #5	$13.26	4.292%	$13.8291	$13.83	$13.85	$13.80
Purchase #6	$231.77	6.503%	$246.842	$246.84	$246.85	$246.80
Purchase #7	$47.40	10.445%	$52.3509	$52.35	$52.35	$52.40
7 purchase totals =	$1,009.52		$1,079.5199	$1,079.52	$1,079.55	$1,079.50