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	$39.79	12.115%	$44.6106	$44.61	$44.60	$44.60
Purchase #2	$246.80	5.622%	$260.6751	$260.68	$260.70	$260.70
Purchase #3	$181.71	4.165%	$189.2782	$189.28	$189.30	$189.30
Purchase #4	$148.51	13.532%	$168.6064	$168.61	$168.60	$168.60
Purchase #5	$215.29	6.706%	$229.7273	$229.73	$229.75	$229.70
Purchase #6	$10.72	12.465%	$12.0562	$12.06	$12.05	$12.10
Purchase #7	$127.87	10.666%	$141.5086	$141.51	$141.50	$141.50
7 purchase totals =	$970.69		$1,046.4624	$1,046.48	$1,046.50	$1,046.50