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	$72.36	5.248%	$76.1575	$76.16	$76.15	$76.20
Purchase #2	$175.96	5.841%	$186.2378	$186.24	$186.25	$186.20
Purchase #3	$71.99	8.773%	$78.3057	$78.31	$78.30	$78.30
Purchase #4	$125.25	12.140%	$140.4554	$140.46	$140.45	$140.50
Purchase #5	$157.32	5.611%	$166.1472	$166.15	$166.15	$166.10
Purchase #6	$175.71	6.121%	$186.4652	$186.47	$186.45	$186.50
Purchase #7	$60.44	8.735%	$65.7194	$65.72	$65.70	$65.70
7 purchase totals =	$839.03		$899.4882	$899.51	$899.45	$899.50