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	$105.46	3.607%	$109.2639	$109.26	$109.25	$109.30
Purchase #2	$235.80	3.870%	$244.9255	$244.93	$244.95	$244.90
Purchase #3	$56.54	4.607%	$59.1448	$59.14	$59.15	$59.10
Purchase #4	$93.25	7.138%	$99.9062	$99.91	$99.90	$99.90
Purchase #5	$141.92	3.231%	$146.5054	$146.51	$146.50	$146.50
Purchase #6	$43.82	10.798%	$48.5517	$48.55	$48.55	$48.60
Purchase #7	$201.90	3.102%	$208.1629	$208.16	$208.15	$208.20
7 purchase totals =	$878.69		$916.4604	$916.46	$916.45	$916.50