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	$173.56	3.711%	$180.0008	$180.00	$180.00	$180.00
Purchase #2	$234.41	3.378%	$242.3284	$242.33	$242.35	$242.30
Purchase #3	$81.79	10.351%	$90.2561	$90.26	$90.25	$90.30
Purchase #4	$135.39	5.322%	$142.5955	$142.60	$142.60	$142.60
Purchase #5	$230.77	11.653%	$257.6616	$257.66	$257.65	$257.70
Purchase #6	$34.25	11.817%	$38.2973	$38.30	$38.30	$38.30
Purchase #7	$171.29	3.224%	$176.8124	$176.81	$176.80	$176.80
7 purchase totals =	$1,061.46		$1,127.9521	$1,127.96	$1,127.95	$1,128.00