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	$221.39	5.507%	$233.5819	$233.58	$233.60	$233.60
Purchase #2	$57.89	11.117%	$64.3256	$64.33	$64.35	$64.30
Purchase #3	$82.88	4.186%	$86.3494	$86.35	$86.35	$86.30
Purchase #4	$81.46	10.294%	$89.8455	$89.85	$89.85	$89.80
Purchase #5	$83.71	3.349%	$86.5134	$86.51	$86.50	$86.50
Purchase #6	$168.93	5.172%	$177.6671	$177.67	$177.65	$177.70
Purchase #7	$97.96	5.230%	$103.0833	$103.08	$103.10	$103.10
7 purchase totals =	$794.22		$841.3662	$841.37	$841.40	$841.30