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	$243.60	4.504%	$254.5717	$254.57	$254.55	$254.60
Purchase #2	$60.47	10.110%	$66.5835	$66.58	$66.60	$66.60
Purchase #3	$180.85	6.658%	$192.891	$192.89	$192.90	$192.90
Purchase #4	$227.98	4.228%	$237.619	$237.62	$237.60	$237.60
Purchase #5	$46.91	7.355%	$50.3602	$50.36	$50.35	$50.40
Purchase #6	$206.76	11.874%	$231.3107	$231.31	$231.30	$231.30
Purchase #7	$38.45	3.753%	$39.893	$39.89	$39.90	$39.90
7 purchase totals =	$1,005.02		$1,073.2291	$1,073.22	$1,073.20	$1,073.30