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	$98.42	3.747%	$102.1078	$102.11	$102.10	$102.10
Purchase #2	$62.55	13.764%	$71.1594	$71.16	$71.15	$71.20
Purchase #3	$71.62	11.808%	$80.0769	$80.08	$80.10	$80.10
Purchase #4	$93.80	12.518%	$105.5419	$105.54	$105.55	$105.50
Purchase #5	$213.72	10.723%	$236.6372	$236.64	$236.65	$236.60
Purchase #6	$147.61	3.307%	$152.4915	$152.49	$152.50	$152.50
Purchase #7	$113.48	12.157%	$127.2758	$127.28	$127.30	$127.30
7 purchase totals =	$801.20		$875.2905	$875.30	$875.35	$875.30