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	$14.46	5.411%	$15.2424	$15.24	$15.25	$15.20
Purchase #2	$11.93	12.765%	$13.4529	$13.45	$13.45	$13.50
Purchase #3	$64.99	13.317%	$73.6447	$73.64	$73.65	$73.60
Purchase #4	$242.78	12.164%	$272.3118	$272.31	$272.30	$272.30
Purchase #5	$37.91	12.780%	$42.7549	$42.75	$42.75	$42.80
Purchase #6	$67.29	7.717%	$72.4828	$72.48	$72.50	$72.50
Purchase #7	$10.62	13.641%	$12.0687	$12.07	$12.05	$12.10
7 purchase totals =	$449.98		$501.9582	$501.94	$501.95	$502.00