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	$88.66	7.389%	$95.2111	$95.21	$95.20	$95.20
Purchase #2	$83.49	6.292%	$88.7432	$88.74	$88.75	$88.70
Purchase #3	$236.67	4.815%	$248.0657	$248.07	$248.05	$248.10
Purchase #4	$172.80	10.213%	$190.4481	$190.45	$190.45	$190.40
Purchase #5	$53.26	5.337%	$56.1025	$56.10	$56.10	$56.10
Purchase #6	$79.25	7.800%	$85.4315	$85.43	$85.45	$85.40
Purchase #7	$64.63	12.271%	$72.5607	$72.56	$72.55	$72.60
7 purchase totals =	$778.76		$836.5628	$836.56	$836.55	$836.50