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	$180.63	10.756%	$200.0586	$200.06	$200.05	$200.10
Purchase #2	$39.45	3.846%	$40.9672	$40.97	$40.95	$41.00
Purchase #3	$164.54	10.807%	$182.3218	$182.32	$182.30	$182.30
Purchase #4	$171.60	3.233%	$177.1478	$177.15	$177.15	$177.10
Purchase #5	$242.48	4.557%	$253.5298	$253.53	$253.55	$253.50
Purchase #6	$83.72	7.344%	$89.8684	$89.87	$89.85	$89.90
Purchase #7	$221.91	13.802%	$252.538	$252.54	$252.55	$252.50
7 purchase totals =	$1,104.33		$1,196.4316	$1,196.44	$1,196.40	$1,196.40