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	$164.52	4.203%	$171.4348	$171.43	$171.45	$171.40
Purchase #2	$233.53	6.780%	$249.3633	$249.36	$249.35	$249.40
Purchase #3	$170.42	7.142%	$182.5914	$182.59	$182.60	$182.60
Purchase #4	$35.48	13.756%	$40.3606	$40.36	$40.35	$40.40
Purchase #5	$187.93	12.308%	$211.0604	$211.06	$211.05	$211.10
Purchase #6	$199.89	13.452%	$226.7792	$226.78	$226.80	$226.80
Purchase #7	$68.96	13.364%	$78.1758	$78.18	$78.20	$78.20
7 purchase totals =	$1,060.73		$1,159.7655	$1,159.76	$1,159.80	$1,159.90