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	$75.55	8.651%	$82.0858	$82.09	$82.10	$82.10
Purchase #2	$197.55	6.258%	$209.9127	$209.91	$209.90	$209.90
Purchase #3	$239.83	12.377%	$269.5138	$269.51	$269.50	$269.50
Purchase #4	$120.86	8.517%	$131.1536	$131.15	$131.15	$131.20
Purchase #5	$93.48	4.657%	$97.8334	$97.83	$97.85	$97.80
Purchase #6	$128.85	12.143%	$144.4963	$144.50	$144.50	$144.50
Purchase #7	$132.29	7.567%	$142.3004	$142.30	$142.30	$142.30
7 purchase totals =	$988.41		$1,077.2960	$1,077.29	$1,077.30	$1,077.30