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	$171.69	12.621%	$193.359	$193.36	$193.35	$193.40
Purchase #2	$225.33	13.314%	$255.3304	$255.33	$255.35	$255.30
Purchase #3	$18.80	10.723%	$20.8159	$20.82	$20.80	$20.80
Purchase #4	$124.41	6.211%	$132.1371	$132.14	$132.15	$132.10
Purchase #5	$164.50	5.566%	$173.6561	$173.66	$173.65	$173.70
Purchase #6	$158.60	5.804%	$167.8051	$167.81	$167.80	$167.80
Purchase #7	$164.53	9.740%	$180.5552	$180.56	$180.55	$180.60
7 purchase totals =	$1,027.86		$1,123.6588	$1,123.68	$1,123.65	$1,123.70