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	$113.73	9.770%	$124.8414	$124.84	$124.85	$124.80
Purchase #2	$73.73	7.201%	$79.0393	$79.04	$79.05	$79.00
Purchase #3	$224.80	5.210%	$236.5121	$236.51	$236.50	$236.50
Purchase #4	$86.97	4.756%	$91.1063	$91.11	$91.10	$91.10
Purchase #5	$240.37	13.706%	$273.3151	$273.32	$273.30	$273.30
Purchase #6	$53.27	11.184%	$59.2277	$59.23	$59.25	$59.20
Purchase #7	$146.30	8.587%	$158.8628	$158.86	$158.85	$158.90
7 purchase totals =	$939.17		$1,022.9047	$1,022.91	$1,022.90	$1,022.80