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	$225.53	9.855%	$247.756	$247.76	$247.75	$247.80
Purchase #2	$237.89	7.753%	$256.3336	$256.33	$256.35	$256.30
Purchase #3	$83.89	12.787%	$94.617	$94.62	$94.60	$94.60
Purchase #4	$113.86	5.801%	$120.465	$120.47	$120.45	$120.50
Purchase #5	$250.32	8.239%	$270.9439	$270.94	$270.95	$270.90
Purchase #6	$39.75	5.806%	$42.0579	$42.06	$42.05	$42.10
Purchase #7	$125.89	6.622%	$134.2264	$134.23	$134.25	$134.20
7 purchase totals =	$1,077.13		$1,166.3998	$1,166.41	$1,166.40	$1,166.40