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	$218.67	3.871%	$227.1347	$227.13	$227.15	$227.10
Purchase #2	$93.86	12.765%	$105.8412	$105.84	$105.85	$105.80
Purchase #3	$209.73	13.328%	$237.6828	$237.68	$237.70	$237.70
Purchase #4	$31.83	5.617%	$33.6179	$33.62	$33.60	$33.60
Purchase #5	$96.84	4.412%	$101.1126	$101.11	$101.10	$101.10
Purchase #6	$191.94	11.504%	$214.0208	$214.02	$214.00	$214.00
Purchase #7	$95.78	4.463%	$100.0547	$100.05	$100.05	$100.10
7 purchase totals =	$938.65		$1,019.4647	$1,019.45	$1,019.45	$1,019.40