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	$68.85	8.144%	$74.4571	$74.46	$74.45	$74.50
Purchase #2	$19.79	4.538%	$20.6881	$20.69	$20.70	$20.70
Purchase #3	$242.53	8.484%	$263.1062	$263.11	$263.10	$263.10
Purchase #4	$187.64	4.660%	$196.384	$196.38	$196.40	$196.40
Purchase #5	$61.38	6.728%	$65.5096	$65.51	$65.50	$65.50
Purchase #6	$110.80	6.596%	$118.1084	$118.11	$118.10	$118.10
Purchase #7	$99.39	13.431%	$112.7391	$112.74	$112.75	$112.70
7 purchase totals =	$790.38		$850.9925	$851.00	$851.00	$851.00