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	$84.52	12.330%	$94.9413	$94.94	$94.95	$94.90
Purchase #2	$78.79	5.804%	$83.363	$83.36	$83.35	$83.40
Purchase #3	$27.72	12.490%	$31.1822	$31.18	$31.20	$31.20
Purchase #4	$6.99	13.165%	$7.9102	$7.91	$7.90	$7.90
Purchase #5	$38.98	6.123%	$41.3667	$41.37	$41.35	$41.40
Purchase #6	$188.44	6.279%	$200.2721	$200.27	$200.25	$200.30
Purchase #7	$91.98	11.639%	$102.6856	$102.69	$102.70	$102.70
7 purchase totals =	$517.42		$561.7211	$561.72	$561.70	$561.80