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	$68.74	6.637%	$73.3023	$73.30	$73.30	$73.30
Purchase #2	$37.47	8.133%	$40.5174	$40.52	$40.50	$40.50
Purchase #3	$181.76	10.531%	$200.9011	$200.90	$200.90	$200.90
Purchase #4	$152.52	12.700%	$171.89	$171.89	$171.90	$171.90
Purchase #5	$211.74	12.829%	$238.9041	$238.90	$238.90	$238.90
Purchase #6	$182.46	9.206%	$199.2573	$199.26	$199.25	$199.30
Purchase #7	$15.77	12.565%	$17.7515	$17.75	$17.75	$17.80
7 purchase totals =	$850.46		$942.5237	$942.52	$942.50	$942.60