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	$204.84	6.738%	$218.6421	$218.64	$218.65	$218.60
Purchase #2	$41.49	10.804%	$45.9726	$45.97	$45.95	$46.00
Purchase #3	$192.34	3.870%	$199.7836	$199.78	$199.80	$199.80
Purchase #4	$165.48	3.600%	$171.4373	$171.44	$171.45	$171.40
Purchase #5	$171.87	11.277%	$191.2518	$191.25	$191.25	$191.30
Purchase #6	$160.48	9.239%	$175.3067	$175.31	$175.30	$175.30
Purchase #7	$81.64	4.440%	$85.2648	$85.26	$85.25	$85.30
7 purchase totals =	$1,018.14		$1,087.6589	$1,087.65	$1,087.65	$1,087.70