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	$65.73	10.860%	$72.8683	$72.87	$72.85	$72.90
Purchase #2	$150.71	11.280%	$167.7101	$167.71	$167.70	$167.70
Purchase #3	$200.64	13.691%	$228.1096	$228.11	$228.10	$228.10
Purchase #4	$109.85	9.808%	$120.6241	$120.62	$120.60	$120.60
Purchase #5	$203.66	9.193%	$222.3825	$222.38	$222.40	$222.40
Purchase #6	$101.97	3.109%	$105.1402	$105.14	$105.15	$105.10
Purchase #7	$239.33	10.167%	$263.6627	$263.66	$263.65	$263.70
7 purchase totals =	$1,071.89		$1,180.4975	$1,180.49	$1,180.45	$1,180.50