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	$199.54	9.329%	$218.1551	$218.16	$218.15	$218.20
Purchase #2	$52.33	6.581%	$55.7738	$55.77	$55.75	$55.80
Purchase #3	$177.72	3.398%	$183.7589	$183.76	$183.75	$183.80
Purchase #4	$221.97	5.199%	$233.5102	$233.51	$233.50	$233.50
Purchase #5	$141.37	7.570%	$152.0717	$152.07	$152.05	$152.10
Purchase #6	$23.28	5.279%	$24.509	$24.51	$24.50	$24.50
Purchase #7	$192.71	12.461%	$216.7236	$216.72	$216.70	$216.70
7 purchase totals =	$1,008.92		$1,084.5023	$1,084.50	$1,084.40	$1,084.60