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	$221.34	6.275%	$235.2291	$235.23	$235.25	$235.20
Purchase #2	$79.65	3.658%	$82.5636	$82.56	$82.55	$82.60
Purchase #3	$53.76	7.151%	$57.6044	$57.60	$57.60	$57.60
Purchase #4	$92.91	6.224%	$98.6927	$98.69	$98.70	$98.70
Purchase #5	$134.88	13.443%	$153.0119	$153.01	$153.00	$153.00
Purchase #6	$94.45	9.572%	$103.4908	$103.49	$103.50	$103.50
Purchase #7	$162.51	6.793%	$173.5493	$173.55	$173.55	$173.50
7 purchase totals =	$839.50		$904.1418	$904.13	$904.15	$904.10