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	$210.83	3.426%	$218.053	$218.05	$218.05	$218.10
Purchase #2	$204.72	8.345%	$221.8039	$221.80	$221.80	$221.80
Purchase #3	$57.50	6.473%	$61.222	$61.22	$61.20	$61.20
Purchase #4	$19.48	3.147%	$20.093	$20.09	$20.10	$20.10
Purchase #5	$159.94	9.208%	$174.6673	$174.67	$174.65	$174.70
Purchase #6	$123.62	12.830%	$139.4804	$139.48	$139.50	$139.50
Purchase #7	$156.73	12.179%	$175.8181	$175.82	$175.80	$175.80
7 purchase totals =	$932.82		$1,011.1377	$1,011.13	$1,011.10	$1,011.20