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	$40.38	10.284%	$44.5327	$44.53	$44.55	$44.50
Purchase #2	$156.56	6.345%	$166.4937	$166.49	$166.50	$166.50
Purchase #3	$52.86	5.338%	$55.6817	$55.68	$55.70	$55.70
Purchase #4	$6.50	9.752%	$7.1339	$7.13	$7.15	$7.10
Purchase #5	$216.95	12.438%	$243.9342	$243.93	$243.95	$243.90
Purchase #6	$209.60	6.815%	$223.8842	$223.88	$223.90	$223.90
Purchase #7	$210.86	8.275%	$228.3087	$228.31	$228.30	$228.30
7 purchase totals =	$893.71		$969.9691	$969.95	$970.05	$969.90