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	$167.83	9.195%	$183.262	$183.26	$183.25	$183.30
Purchase #2	$222.73	5.676%	$235.3722	$235.37	$235.35	$235.40
Purchase #3	$233.48	12.567%	$262.8214	$262.82	$262.80	$262.80
Purchase #4	$173.27	5.134%	$182.1657	$182.17	$182.15	$182.20
Purchase #5	$32.86	10.837%	$36.421	$36.42	$36.40	$36.40
Purchase #6	$147.91	5.115%	$155.4756	$155.48	$155.50	$155.50
Purchase #7	$179.30	11.719%	$200.3122	$200.31	$200.30	$200.30
7 purchase totals =	$1,157.38		$1,255.8301	$1,255.83	$1,255.75	$1,255.90