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	$69.50	3.819%	$72.1542	$72.15	$72.15	$72.20
Purchase #2	$159.92	4.133%	$166.5295	$166.53	$166.55	$166.50
Purchase #3	$18.71	11.443%	$20.851	$20.85	$20.85	$20.90
Purchase #4	$162.94	7.231%	$174.7222	$174.72	$174.70	$174.70
Purchase #5	$195.53	13.806%	$222.5249	$222.52	$222.50	$222.50
Purchase #6	$143.70	13.348%	$162.8811	$162.88	$162.90	$162.90
Purchase #7	$5.99	9.409%	$6.5536	$6.55	$6.55	$6.60
7 purchase totals =	$756.29		$826.2165	$826.20	$826.20	$826.30