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	$233.37	8.186%	$252.4737	$252.47	$252.45	$252.50
Purchase #2	$162.62	11.205%	$180.8416	$180.84	$180.85	$180.80
Purchase #3	$87.63	3.282%	$90.506	$90.51	$90.50	$90.50
Purchase #4	$111.92	6.814%	$119.5462	$119.55	$119.55	$119.50
Purchase #5	$231.33	4.871%	$242.5981	$242.60	$242.60	$242.60
Purchase #6	$210.78	7.579%	$226.755	$226.76	$226.75	$226.80
Purchase #7	$89.58	11.333%	$99.7321	$99.73	$99.75	$99.70
7 purchase totals =	$1,127.23		$1,212.4527	$1,212.46	$1,212.45	$1,212.40