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	$164.54	5.367%	$173.3709	$173.37	$173.35	$173.40
Purchase #2	$93.73	6.615%	$99.9302	$99.93	$99.95	$99.90
Purchase #3	$89.54	13.243%	$101.3978	$101.40	$101.40	$101.40
Purchase #4	$68.85	4.700%	$72.086	$72.09	$72.10	$72.10
Purchase #5	$216.61	11.527%	$241.5786	$241.58	$241.60	$241.60
Purchase #6	$161.28	4.345%	$168.2876	$168.29	$168.30	$168.30
Purchase #7	$41.44	5.450%	$43.6985	$43.70	$43.70	$43.70
7 purchase totals =	$835.99		$900.3496	$900.36	$900.40	$900.40