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	$197.86	11.314%	$220.2459	$220.25	$220.25	$220.20
Purchase #2	$100.78	10.453%	$111.3145	$111.31	$111.30	$111.30
Purchase #3	$159.85	6.501%	$170.2418	$170.24	$170.25	$170.20
Purchase #4	$244.28	11.827%	$273.171	$273.17	$273.15	$273.20
Purchase #5	$123.90	12.728%	$139.67	$139.67	$139.65	$139.70
Purchase #6	$20.30	7.669%	$21.8568	$21.86	$21.85	$21.90
Purchase #7	$72.25	3.451%	$74.7433	$74.74	$74.75	$74.70
7 purchase totals =	$919.22		$1,011.2433	$1,011.24	$1,011.20	$1,011.20