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	$217.52	3.157%	$224.3871	$224.39	$224.40	$224.40
Purchase #2	$104.46	4.464%	$109.1231	$109.12	$109.10	$109.10
Purchase #3	$28.82	5.540%	$30.4166	$30.42	$30.40	$30.40
Purchase #4	$31.48	12.625%	$35.4544	$35.45	$35.45	$35.50
Purchase #5	$64.93	9.285%	$70.9588	$70.96	$70.95	$71.00
Purchase #6	$42.63	11.515%	$47.5388	$47.54	$47.55	$47.50
Purchase #7	$137.64	8.853%	$149.8253	$149.83	$149.85	$149.80
7 purchase totals =	$627.48		$667.7041	$667.71	$667.70	$667.70