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	$217.34	4.367%	$226.8312	$226.83	$226.85	$226.80
Purchase #2	$223.72	3.277%	$231.0513	$231.05	$231.05	$231.10
Purchase #3	$137.46	7.256%	$147.4341	$147.43	$147.45	$147.40
Purchase #4	$164.38	4.306%	$171.4582	$171.46	$171.45	$171.50
Purchase #5	$144.56	4.146%	$150.5535	$150.55	$150.55	$150.60
Purchase #6	$224.87	11.562%	$250.8695	$250.87	$250.85	$250.90
Purchase #7	$28.87	9.316%	$31.5595	$31.56	$31.55	$31.60
7 purchase totals =	$1,141.20		$1,209.7573	$1,209.75	$1,209.75	$1,209.90