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	$190.76	4.372%	$199.1	$199.10	$199.10	$199.10
Purchase #2	$103.87	7.639%	$111.8046	$111.80	$111.80	$111.80
Purchase #3	$85.43	5.464%	$90.0979	$90.10	$90.10	$90.10
Purchase #4	$36.95	8.771%	$40.1909	$40.19	$40.20	$40.20
Purchase #5	$143.69	10.196%	$158.3406	$158.34	$158.35	$158.30
Purchase #6	$83.35	3.367%	$86.1564	$86.16	$86.15	$86.20
Purchase #7	$193.43	3.573%	$200.3413	$200.34	$200.35	$200.30
7 purchase totals =	$837.48		$886.0317	$886.03	$886.05	$886.00