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	$136.40	8.796%	$148.3977	$148.40	$148.40	$148.40
Purchase #2	$161.42	11.344%	$179.7315	$179.73	$179.75	$179.70
Purchase #3	$74.29	8.190%	$80.3744	$80.37	$80.35	$80.40
Purchase #4	$161.65	6.169%	$171.6222	$171.62	$171.60	$171.60
Purchase #5	$106.97	10.404%	$118.0992	$118.10	$118.10	$118.10
Purchase #6	$231.37	8.227%	$250.4048	$250.40	$250.40	$250.40
Purchase #7	$85.61	3.108%	$88.2708	$88.27	$88.25	$88.30
7 purchase totals =	$957.71		$1,036.9006	$1,036.89	$1,036.85	$1,036.90