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	$152.52	11.777%	$170.4823	$170.48	$170.50	$170.50
Purchase #2	$153.41	12.699%	$172.8915	$172.89	$172.90	$172.90
Purchase #3	$197.34	7.548%	$212.2352	$212.24	$212.25	$212.20
Purchase #4	$43.33	12.355%	$48.6834	$48.68	$48.70	$48.70
Purchase #5	$190.57	7.423%	$204.716	$204.72	$204.70	$204.70
Purchase #6	$101.82	3.133%	$105.01	$105.01	$105.00	$105.00
Purchase #7	$84.48	7.254%	$90.6082	$90.61	$90.60	$90.60
7 purchase totals =	$923.47		$1,004.6266	$1,004.63	$1,004.65	$1,004.60