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	$186.94	4.690%	$195.7075	$195.71	$195.70	$195.70
Purchase #2	$105.77	3.805%	$109.7945	$109.79	$109.80	$109.80
Purchase #3	$94.35	13.807%	$107.3769	$107.38	$107.40	$107.40
Purchase #4	$109.49	6.111%	$116.1809	$116.18	$116.20	$116.20
Purchase #5	$166.41	9.247%	$181.7979	$181.80	$181.80	$181.80
Purchase #6	$138.86	9.387%	$151.8948	$151.89	$151.90	$151.90
Purchase #7	$132.78	5.613%	$140.2329	$140.23	$140.25	$140.20
7 purchase totals =	$934.60		$1,002.9854	$1,002.98	$1,003.05	$1,003.00