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	$11.49	4.135%	$11.9651	$11.97	$11.95	$12.00
Purchase #2	$27.90	9.487%	$30.5469	$30.55	$30.55	$30.50
Purchase #3	$18.86	10.110%	$20.7667	$20.77	$20.75	$20.80
Purchase #4	$94.29	11.533%	$105.1645	$105.16	$105.15	$105.20
Purchase #5	$103.64	12.448%	$116.5411	$116.54	$116.55	$116.50
Purchase #6	$61.76	12.451%	$69.4497	$69.45	$69.45	$69.40
Purchase #7	$46.57	7.379%	$50.0064	$50.01	$50.00	$50.00
7 purchase totals =	$364.51		$404.4404	$404.45	$404.40	$404.40