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	$198.76	7.534%	$213.7346	$213.73	$213.75	$213.70
Purchase #2	$85.87	5.461%	$90.5594	$90.56	$90.55	$90.60
Purchase #3	$153.35	13.692%	$174.3467	$174.35	$174.35	$174.30
Purchase #4	$99.52	3.265%	$102.7693	$102.77	$102.75	$102.80
Purchase #5	$148.28	4.553%	$155.0312	$155.03	$155.05	$155.00
Purchase #6	$158.33	10.179%	$174.4464	$174.45	$174.45	$174.40
Purchase #7	$148.94	3.822%	$154.6325	$154.63	$154.65	$154.60
7 purchase totals =	$993.05		$1,065.5201	$1,065.52	$1,065.55	$1,065.40