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	$70.58	3.810%	$73.2691	$73.27	$73.25	$73.30
Purchase #2	$93.97	5.367%	$99.0134	$99.01	$99.00	$99.00
Purchase #3	$242.67	5.750%	$256.6235	$256.62	$256.60	$256.60
Purchase #4	$107.69	3.111%	$111.0402	$111.04	$111.05	$111.00
Purchase #5	$72.89	6.776%	$77.829	$77.83	$77.85	$77.80
Purchase #6	$179.33	11.874%	$200.6236	$200.62	$200.60	$200.60
Purchase #7	$246.25	8.666%	$267.59	$267.59	$267.60	$267.60
7 purchase totals =	$1,013.38		$1,085.9888	$1,085.98	$1,085.95	$1,085.90