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	$44.33	12.263%	$49.7662	$49.77	$49.75	$49.80
Purchase #2	$170.64	3.218%	$176.1312	$176.13	$176.15	$176.10
Purchase #3	$172.55	5.758%	$182.4854	$182.49	$182.50	$182.50
Purchase #4	$172.32	5.180%	$181.2462	$181.25	$181.25	$181.20
Purchase #5	$183.86	4.365%	$191.8855	$191.89	$191.90	$191.90
Purchase #6	$219.37	6.490%	$233.6071	$233.61	$233.60	$233.60
Purchase #7	$75.71	5.507%	$79.8793	$79.88	$79.90	$79.90
7 purchase totals =	$1,038.78		$1,095.0009	$1,095.02	$1,095.05	$1,095.00