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	$204.85	4.170%	$213.3922	$213.39	$213.40	$213.40
Purchase #2	$196.81	8.350%	$213.2436	$213.24	$213.25	$213.20
Purchase #3	$104.28	5.807%	$110.3355	$110.34	$110.35	$110.30
Purchase #4	$79.47	5.179%	$83.5858	$83.59	$83.60	$83.60
Purchase #5	$144.38	5.801%	$152.7555	$152.76	$152.75	$152.80
Purchase #6	$29.67	13.689%	$33.7315	$33.73	$33.75	$33.70
Purchase #7	$65.94	9.757%	$72.3738	$72.37	$72.35	$72.40
7 purchase totals =	$825.40		$879.4179	$879.42	$879.45	$879.40