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	$35.35	4.779%	$37.0394	$37.04	$37.05	$37.00
Purchase #2	$17.77	4.449%	$18.5606	$18.56	$18.55	$18.60
Purchase #3	$91.37	9.607%	$100.1479	$100.15	$100.15	$100.10
Purchase #4	$22.84	11.340%	$25.4301	$25.43	$25.45	$25.40
Purchase #5	$178.76	11.299%	$198.9581	$198.96	$198.95	$199.00
Purchase #6	$210.63	12.394%	$236.7355	$236.74	$236.75	$236.70
Purchase #7	$11.86	13.446%	$13.4547	$13.45	$13.45	$13.50
7 purchase totals =	$568.58		$630.3263	$630.33	$630.35	$630.30