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	$32.64	12.630%	$36.7624	$36.76	$36.75	$36.80
Purchase #2	$75.71	13.752%	$86.1216	$86.12	$86.10	$86.10
Purchase #3	$248.80	9.782%	$273.1376	$273.14	$273.15	$273.10
Purchase #4	$36.49	4.183%	$38.0164	$38.02	$38.00	$38.00
Purchase #5	$38.53	9.651%	$42.2485	$42.25	$42.25	$42.20
Purchase #6	$112.89	13.629%	$128.2758	$128.28	$128.30	$128.30
Purchase #7	$128.65	3.152%	$132.705	$132.71	$132.70	$132.70
7 purchase totals =	$673.71		$737.2673	$737.28	$737.25	$737.20