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	$69.65	12.467%	$78.3333	$78.33	$78.35	$78.30
Purchase #2	$23.53	3.689%	$24.398	$24.40	$24.40	$24.40
Purchase #3	$52.77	12.868%	$59.5604	$59.56	$59.55	$59.60
Purchase #4	$227.95	8.146%	$246.5188	$246.52	$246.50	$246.50
Purchase #5	$240.50	4.317%	$250.8824	$250.88	$250.90	$250.90
Purchase #6	$37.98	13.642%	$43.1612	$43.16	$43.15	$43.20
Purchase #7	$174.46	9.616%	$191.2361	$191.24	$191.25	$191.20
7 purchase totals =	$826.84		$894.0902	$894.09	$894.10	$894.10