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	$235.45	7.614%	$253.3772	$253.38	$253.40	$253.40
Purchase #2	$38.59	13.132%	$43.6576	$43.66	$43.65	$43.70
Purchase #3	$186.52	13.104%	$210.9616	$210.96	$210.95	$211.00
Purchase #4	$90.39	11.601%	$100.8761	$100.88	$100.90	$100.90
Purchase #5	$147.98	3.480%	$153.1297	$153.13	$153.15	$153.10
Purchase #6	$45.78	9.295%	$50.0353	$50.04	$50.05	$50.00
Purchase #7	$175.81	12.787%	$198.2908	$198.29	$198.30	$198.30
7 purchase totals =	$920.52		$1,010.3283	$1,010.34	$1,010.40	$1,010.40