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	$44.33	4.419%	$46.2889	$46.29	$46.30	$46.30
Purchase #2	$71.25	9.677%	$78.1449	$78.14	$78.15	$78.10
Purchase #3	$99.62	4.859%	$104.4605	$104.46	$104.45	$104.50
Purchase #4	$229.82	6.676%	$245.1628	$245.16	$245.15	$245.20
Purchase #5	$223.84	3.537%	$231.7572	$231.76	$231.75	$231.80
Purchase #6	$53.77	7.654%	$57.8856	$57.89	$57.90	$57.90
Purchase #7	$146.45	9.565%	$160.4579	$160.46	$160.45	$160.50
7 purchase totals =	$869.08		$924.1578	$924.16	$924.15	$924.30