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	$82.39	6.267%	$87.5534	$87.55	$87.55	$87.60
Purchase #2	$67.76	8.410%	$73.4586	$73.46	$73.45	$73.50
Purchase #3	$163.46	8.123%	$176.7379	$176.74	$176.75	$176.70
Purchase #4	$123.36	3.221%	$127.3334	$127.33	$127.35	$127.30
Purchase #5	$105.94	4.754%	$110.9764	$110.98	$111.00	$111.00
Purchase #6	$63.27	13.191%	$71.6159	$71.62	$71.60	$71.60
Purchase #7	$155.64	9.466%	$170.3729	$170.37	$170.35	$170.40
7 purchase totals =	$761.82		$818.0485	$818.05	$818.05	$818.10