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	$67.54	6.234%	$71.7504	$71.75	$71.75	$71.80
Purchase #2	$20.64	5.603%	$21.7965	$21.80	$21.80	$21.80
Purchase #3	$156.61	11.345%	$174.3774	$174.38	$174.40	$174.40
Purchase #4	$199.83	11.258%	$222.3269	$222.33	$222.35	$222.30
Purchase #5	$94.69	8.517%	$102.7547	$102.75	$102.75	$102.80
Purchase #6	$37.45	12.482%	$42.1245	$42.12	$42.10	$42.10
Purchase #7	$96.70	6.505%	$102.9903	$102.99	$103.00	$103.00
7 purchase totals =	$673.46		$738.1207	$738.12	$738.15	$738.20