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	$169.56	9.118%	$185.0205	$185.02	$185.00	$185.00
Purchase #2	$66.52	8.215%	$71.9846	$71.98	$72.00	$72.00
Purchase #3	$80.94	12.222%	$90.8325	$90.83	$90.85	$90.80
Purchase #4	$122.71	7.387%	$131.7746	$131.77	$131.75	$131.80
Purchase #5	$219.98	10.463%	$242.9965	$243.00	$243.00	$243.00
Purchase #6	$189.71	3.794%	$196.9076	$196.91	$196.90	$196.90
Purchase #7	$236.90	12.737%	$267.074	$267.07	$267.05	$267.10
7 purchase totals =	$1,086.32		$1,186.5903	$1,186.58	$1,186.55	$1,186.60