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	$181.33	10.234%	$199.8873	$199.89	$199.90	$199.90
Purchase #2	$105.67	3.166%	$109.0155	$109.02	$109.00	$109.00
Purchase #3	$114.59	6.349%	$121.8653	$121.87	$121.85	$121.90
Purchase #4	$111.67	12.142%	$125.229	$125.23	$125.25	$125.20
Purchase #5	$63.83	12.758%	$71.9734	$71.97	$71.95	$72.00
Purchase #6	$191.52	13.558%	$217.4863	$217.49	$217.50	$217.50
Purchase #7	$30.62	8.243%	$33.144	$33.14	$33.15	$33.10
7 purchase totals =	$799.23		$878.6008	$878.61	$878.60	$878.60