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	$132.90	13.694%	$151.0993	$151.10	$151.10	$151.10
Purchase #2	$88.86	5.194%	$93.4754	$93.48	$93.50	$93.50
Purchase #3	$40.37	7.496%	$43.3961	$43.40	$43.40	$43.40
Purchase #4	$48.67	11.516%	$54.2748	$54.27	$54.25	$54.30
Purchase #5	$49.57	3.354%	$51.2326	$51.23	$51.25	$51.20
Purchase #6	$67.34	7.668%	$72.5036	$72.50	$72.50	$72.50
Purchase #7	$190.25	5.299%	$200.3313	$200.33	$200.35	$200.30
7 purchase totals =	$617.96		$666.3131	$666.31	$666.35	$666.30