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	$31.95	13.692%	$36.3246	$36.32	$36.30	$36.30
Purchase #2	$37.33	4.208%	$38.9008	$38.90	$38.90	$38.90
Purchase #3	$80.57	3.374%	$83.2884	$83.29	$83.30	$83.30
Purchase #4	$20.94	9.449%	$22.9186	$22.92	$22.90	$22.90
Purchase #5	$86.76	4.369%	$90.5505	$90.55	$90.55	$90.60
Purchase #6	$29.95	4.855%	$31.4041	$31.40	$31.40	$31.40
Purchase #7	$94.55	10.500%	$104.4778	$104.48	$104.50	$104.50
7 purchase totals =	$382.05		$407.8648	$407.86	$407.85	$407.90