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	$183.25	12.858%	$206.8123	$206.81	$206.80	$206.80
Purchase #2	$137.63	3.748%	$142.7884	$142.79	$142.80	$142.80
Purchase #3	$152.61	11.663%	$170.4089	$170.41	$170.40	$170.40
Purchase #4	$34.71	3.698%	$35.9936	$35.99	$36.00	$36.00
Purchase #5	$147.62	4.224%	$153.8555	$153.86	$153.85	$153.90
Purchase #6	$221.79	3.132%	$228.7365	$228.74	$228.75	$228.70
Purchase #7	$73.31	6.747%	$78.2562	$78.26	$78.25	$78.30
7 purchase totals =	$950.92		$1,016.8514	$1,016.86	$1,016.85	$1,016.90