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	$87.58	10.301%	$96.6016	$96.60	$96.60	$96.60
Purchase #2	$242.54	3.392%	$250.767	$250.77	$250.75	$250.80
Purchase #3	$220.26	13.216%	$249.3696	$249.37	$249.35	$249.40
Purchase #4	$89.76	4.412%	$93.7202	$93.72	$93.70	$93.70
Purchase #5	$78.59	13.264%	$89.0142	$89.01	$89.00	$89.00
Purchase #6	$191.89	4.478%	$200.4828	$200.48	$200.50	$200.50
Purchase #7	$49.86	9.463%	$54.5783	$54.58	$54.60	$54.60
7 purchase totals =	$960.48		$1,034.5337	$1,034.53	$1,034.50	$1,034.60