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	$64.33	7.207%	$68.9663	$68.97	$68.95	$69.00
Purchase #2	$123.93	13.798%	$141.0299	$141.03	$141.05	$141.00
Purchase #3	$49.49	11.661%	$55.261	$55.26	$55.25	$55.30
Purchase #4	$227.86	7.546%	$245.0543	$245.05	$245.05	$245.10
Purchase #5	$102.48	8.471%	$111.1611	$111.16	$111.15	$111.20
Purchase #6	$105.61	6.194%	$112.1515	$112.15	$112.15	$112.20
Purchase #7	$96.37	3.680%	$99.9164	$99.92	$99.90	$99.90
7 purchase totals =	$770.07		$833.5405	$833.54	$833.50	$833.70