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	$80.45	13.304%	$91.1531	$91.15	$91.15	$91.20
Purchase #2	$199.32	5.804%	$210.8885	$210.89	$210.90	$210.90
Purchase #3	$50.56	3.280%	$52.2184	$52.22	$52.20	$52.20
Purchase #4	$105.56	7.150%	$113.1075	$113.11	$113.10	$113.10
Purchase #5	$87.89	5.624%	$92.8329	$92.83	$92.85	$92.80
Purchase #6	$43.33	4.424%	$45.2469	$45.25	$45.25	$45.20
Purchase #7	$150.76	3.571%	$156.1436	$156.14	$156.15	$156.10
7 purchase totals =	$717.87		$761.5909	$761.59	$761.60	$761.50