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	$186.70	3.591%	$193.4044	$193.40	$193.40	$193.40
Purchase #2	$185.57	5.407%	$195.6038	$195.60	$195.60	$195.60
Purchase #3	$60.39	10.469%	$66.7122	$66.71	$66.70	$66.70
Purchase #4	$200.90	11.119%	$223.2381	$223.24	$223.25	$223.20
Purchase #5	$48.87	10.363%	$53.9344	$53.93	$53.95	$53.90
Purchase #6	$223.75	12.346%	$251.3742	$251.37	$251.35	$251.40
Purchase #7	$64.33	11.756%	$71.8926	$71.89	$71.90	$71.90
7 purchase totals =	$970.51		$1,056.1597	$1,056.14	$1,056.15	$1,056.10