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	$228.90	11.771%	$255.8438	$255.84	$255.85	$255.80
Purchase #2	$228.43	11.302%	$254.2472	$254.25	$254.25	$254.20
Purchase #3	$70.59	11.694%	$78.8448	$78.84	$78.85	$78.80
Purchase #4	$59.33	4.582%	$62.0485	$62.05	$62.05	$62.00
Purchase #5	$132.66	13.377%	$150.4059	$150.41	$150.40	$150.40
Purchase #6	$215.46	10.568%	$238.2298	$238.23	$238.25	$238.20
Purchase #7	$214.57	8.284%	$232.345	$232.35	$232.35	$232.30
7 purchase totals =	$1,149.94		$1,271.9650	$1,271.97	$1,272.00	$1,271.70