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	$80.42	11.707%	$89.8348	$89.83	$89.85	$89.80
Purchase #2	$70.56	11.752%	$78.8522	$78.85	$78.85	$78.90
Purchase #3	$195.27	8.702%	$212.2624	$212.26	$212.25	$212.30
Purchase #4	$174.59	7.190%	$187.143	$187.14	$187.15	$187.10
Purchase #5	$119.98	6.715%	$128.0367	$128.04	$128.05	$128.00
Purchase #6	$119.92	5.137%	$126.0803	$126.08	$126.10	$126.10
Purchase #7	$227.45	10.290%	$250.8546	$250.85	$250.85	$250.90
7 purchase totals =	$988.19		$1,073.0640	$1,073.05	$1,073.10	$1,073.10