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	$235.75	9.738%	$258.7073	$258.71	$258.70	$258.70
Purchase #2	$164.58	12.496%	$185.1459	$185.15	$185.15	$185.10
Purchase #3	$60.31	11.124%	$67.0189	$67.02	$67.00	$67.00
Purchase #4	$176.48	8.441%	$191.3767	$191.38	$191.40	$191.40
Purchase #5	$76.57	12.326%	$86.008	$86.01	$86.00	$86.00
Purchase #6	$72.78	8.278%	$78.8047	$78.80	$78.80	$78.80
Purchase #7	$7.33	4.103%	$7.6307	$7.63	$7.65	$7.60
7 purchase totals =	$793.80		$874.6922	$874.70	$874.70	$874.60