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	$37.25	11.601%	$41.5714	$41.57	$41.55	$41.60
Purchase #2	$61.87	4.123%	$64.4209	$64.42	$64.40	$64.40
Purchase #3	$90.59	4.778%	$94.9184	$94.92	$94.90	$94.90
Purchase #4	$18.89	7.503%	$20.3073	$20.31	$20.30	$20.30
Purchase #5	$157.37	11.780%	$175.9082	$175.91	$175.90	$175.90
Purchase #6	$27.41	4.450%	$28.6297	$28.63	$28.65	$28.60
Purchase #7	$73.71	3.153%	$76.0341	$76.03	$76.05	$76.00
7 purchase totals =	$467.09		$501.7900	$501.79	$501.75	$501.70