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	$82.62	4.564%	$86.3908	$86.39	$86.40	$86.40
Purchase #2	$176.94	13.411%	$200.6694	$200.67	$200.65	$200.70
Purchase #3	$37.83	8.655%	$41.1042	$41.10	$41.10	$41.10
Purchase #4	$204.53	5.665%	$216.1166	$216.12	$216.10	$216.10
Purchase #5	$157.67	5.134%	$165.7648	$165.76	$165.75	$165.80
Purchase #6	$151.72	4.806%	$159.0117	$159.01	$159.00	$159.00
Purchase #7	$228.56	6.163%	$242.6462	$242.65	$242.65	$242.60
7 purchase totals =	$1,039.87		$1,111.7037	$1,111.70	$1,111.65	$1,111.70