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	$73.53	11.553%	$82.0249	$82.02	$82.00	$82.00
Purchase #2	$142.68	12.826%	$160.9801	$160.98	$161.00	$161.00
Purchase #3	$212.74	9.822%	$233.6353	$233.64	$233.65	$233.60
Purchase #4	$129.62	7.453%	$139.2806	$139.28	$139.30	$139.30
Purchase #5	$118.78	4.157%	$123.7177	$123.72	$123.70	$123.70
Purchase #6	$145.56	5.827%	$154.0418	$154.04	$154.05	$154.00
Purchase #7	$10.32	5.601%	$10.898	$10.90	$10.90	$10.90
7 purchase totals =	$833.23		$904.5784	$904.58	$904.60	$904.50