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	$244.62	4.372%	$255.3148	$255.31	$255.30	$255.30
Purchase #2	$238.77	13.783%	$271.6797	$271.68	$271.70	$271.70
Purchase #3	$37.50	8.299%	$40.6121	$40.61	$40.60	$40.60
Purchase #4	$48.45	10.131%	$53.3585	$53.36	$53.35	$53.40
Purchase #5	$232.26	7.753%	$250.2671	$250.27	$250.25	$250.30
Purchase #6	$112.73	12.785%	$127.1425	$127.14	$127.15	$127.10
Purchase #7	$6.59	5.362%	$6.9434	$6.94	$6.95	$6.90
7 purchase totals =	$920.92		$1,005.3181	$1,005.31	$1,005.30	$1,005.30