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	$182.87	8.579%	$198.5584	$198.56	$198.55	$198.60
Purchase #2	$48.81	3.338%	$50.4393	$50.44	$50.45	$50.40
Purchase #3	$151.79	7.304%	$162.8767	$162.88	$162.90	$162.90
Purchase #4	$158.62	8.824%	$172.6166	$172.62	$172.60	$172.60
Purchase #5	$102.59	10.828%	$113.6984	$113.70	$113.70	$113.70
Purchase #6	$129.49	12.363%	$145.4988	$145.50	$145.50	$145.50
Purchase #7	$165.65	11.439%	$184.5987	$184.60	$184.60	$184.60
7 purchase totals =	$939.82		$1,028.2869	$1,028.30	$1,028.30	$1,028.30