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	$62.96	8.581%	$68.3626	$68.36	$68.35	$68.40
Purchase #2	$40.38	13.433%	$45.8042	$45.80	$45.80	$45.80
Purchase #3	$28.26	12.692%	$31.8468	$31.85	$31.85	$31.80
Purchase #4	$32.39	12.232%	$36.3519	$36.35	$36.35	$36.40
Purchase #5	$172.70	13.590%	$196.1699	$196.17	$196.15	$196.20
Purchase #6	$68.33	8.153%	$73.9009	$73.90	$73.90	$73.90
Purchase #7	$118.54	7.259%	$127.1448	$127.14	$127.15	$127.10
7 purchase totals =	$523.56		$579.5811	$579.57	$579.55	$579.60