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	$89.72	6.845%	$95.8613	$95.86	$95.85	$95.90
Purchase #2	$29.89	12.621%	$33.6624	$33.66	$33.65	$33.70
Purchase #3	$103.96	7.709%	$111.9743	$111.97	$111.95	$112.00
Purchase #4	$62.77	10.256%	$69.2077	$69.21	$69.20	$69.20
Purchase #5	$185.59	8.144%	$200.7044	$200.70	$200.70	$200.70
Purchase #6	$95.89	13.809%	$109.1315	$109.13	$109.15	$109.10
Purchase #7	$181.40	9.658%	$198.9196	$198.92	$198.90	$198.90
7 purchase totals =	$749.22		$819.4612	$819.45	$819.40	$819.50