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	$150.70	11.737%	$168.3877	$168.39	$168.40	$168.40
Purchase #2	$206.32	4.369%	$215.3341	$215.33	$215.35	$215.30
Purchase #3	$231.71	5.819%	$245.1932	$245.19	$245.20	$245.20
Purchase #4	$99.88	11.246%	$111.1125	$111.11	$111.10	$111.10
Purchase #5	$20.25	10.107%	$22.2967	$22.30	$22.30	$22.30
Purchase #6	$181.85	4.624%	$190.2587	$190.26	$190.25	$190.30
Purchase #7	$136.34	5.777%	$144.2164	$144.22	$144.20	$144.20
7 purchase totals =	$1,027.05		$1,096.7993	$1,096.80	$1,096.80	$1,096.80