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	$91.57	12.243%	$102.7809	$102.78	$102.80	$102.80
Purchase #2	$68.71	4.253%	$71.6322	$71.63	$71.65	$71.60
Purchase #3	$5.84	12.865%	$6.5913	$6.59	$6.60	$6.60
Purchase #4	$159.57	9.740%	$175.1121	$175.11	$175.10	$175.10
Purchase #5	$179.26	9.678%	$196.6088	$196.61	$196.60	$196.60
Purchase #6	$31.89	7.114%	$34.1587	$34.16	$34.15	$34.20
Purchase #7	$128.85	7.479%	$138.4867	$138.49	$138.50	$138.50
7 purchase totals =	$665.69		$725.3707	$725.37	$725.40	$725.40