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	$57.87	4.171%	$60.2838	$60.28	$60.30	$60.30
Purchase #2	$237.49	3.165%	$245.0066	$245.01	$245.00	$245.00
Purchase #3	$71.32	10.219%	$78.6082	$78.61	$78.60	$78.60
Purchase #4	$73.87	9.282%	$80.7266	$80.73	$80.75	$80.70
Purchase #5	$156.70	5.853%	$165.8717	$165.87	$165.85	$165.90
Purchase #6	$37.46	13.300%	$42.4422	$42.44	$42.45	$42.40
Purchase #7	$232.64	11.833%	$260.1683	$260.17	$260.15	$260.20
7 purchase totals =	$867.35		$933.1074	$933.11	$933.10	$933.10