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	$82.46	7.402%	$88.5637	$88.56	$88.55	$88.60
Purchase #2	$139.53	4.266%	$145.4823	$145.48	$145.50	$145.50
Purchase #3	$98.46	3.493%	$101.8992	$101.90	$101.90	$101.90
Purchase #4	$54.45	8.638%	$59.1534	$59.15	$59.15	$59.20
Purchase #5	$223.70	9.700%	$245.3989	$245.40	$245.40	$245.40
Purchase #6	$94.98	5.453%	$100.1593	$100.16	$100.15	$100.20
Purchase #7	$145.64	9.212%	$159.0564	$159.06	$159.05	$159.10
7 purchase totals =	$839.22		$899.7132	$899.71	$899.70	$899.90