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	$98.27	13.869%	$111.8991	$111.90	$111.90	$111.90
Purchase #2	$93.66	13.673%	$106.4661	$106.47	$106.45	$106.50
Purchase #3	$59.58	6.139%	$63.2376	$63.24	$63.25	$63.20
Purchase #4	$152.26	6.444%	$162.0716	$162.07	$162.05	$162.10
Purchase #5	$21.33	4.121%	$22.209	$22.21	$22.20	$22.20
Purchase #6	$101.80	3.660%	$105.5259	$105.53	$105.55	$105.50
Purchase #7	$87.48	6.646%	$93.2939	$93.29	$93.30	$93.30
7 purchase totals =	$614.38		$664.7032	$664.71	$664.70	$664.70