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	$10.52	8.208%	$11.3835	$11.38	$11.40	$11.40
Purchase #2	$16.33	10.655%	$18.07	$18.07	$18.05	$18.10
Purchase #3	$28.87	10.525%	$31.9086	$31.91	$31.90	$31.90
Purchase #4	$174.51	3.760%	$181.0716	$181.07	$181.05	$181.10
Purchase #5	$209.46	5.466%	$220.9091	$220.91	$220.90	$220.90
Purchase #6	$85.30	4.140%	$88.8314	$88.83	$88.85	$88.80
Purchase #7	$227.84	6.799%	$243.3308	$243.33	$243.35	$243.30
7 purchase totals =	$752.83		$795.5050	$795.50	$795.50	$795.50