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	$228.48	6.245%	$242.7486	$242.75	$242.75	$242.70
Purchase #2	$213.84	7.386%	$229.6342	$229.63	$229.65	$229.60
Purchase #3	$157.30	5.162%	$165.4198	$165.42	$165.40	$165.40
Purchase #4	$38.67	8.712%	$42.0389	$42.04	$42.05	$42.00
Purchase #5	$180.69	8.869%	$196.7154	$196.72	$196.70	$196.70
Purchase #6	$19.48	8.293%	$21.0955	$21.10	$21.10	$21.10
Purchase #7	$144.41	12.272%	$162.132	$162.13	$162.15	$162.10
7 purchase totals =	$982.87		$1,059.7844	$1,059.79	$1,059.80	$1,059.60