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	$146.75	10.128%	$161.6128	$161.61	$161.60	$161.60
Purchase #2	$84.58	12.744%	$95.3589	$95.36	$95.35	$95.40
Purchase #3	$155.76	7.771%	$167.8641	$167.86	$167.85	$167.90
Purchase #4	$206.85	11.471%	$230.5778	$230.58	$230.60	$230.60
Purchase #5	$196.65	11.810%	$219.8744	$219.87	$219.85	$219.90
Purchase #6	$32.76	12.514%	$36.8596	$36.86	$36.85	$36.90
Purchase #7	$95.75	9.194%	$104.5533	$104.55	$104.55	$104.60
7 purchase totals =	$919.10		$1,016.7009	$1,016.69	$1,016.65	$1,016.90