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	$29.74	10.148%	$32.758	$32.76	$32.75	$32.80
Purchase #2	$102.73	8.380%	$111.3388	$111.34	$111.35	$111.30
Purchase #3	$174.57	6.407%	$185.7547	$185.75	$185.75	$185.80
Purchase #4	$67.28	3.314%	$69.5097	$69.51	$69.50	$69.50
Purchase #5	$222.96	6.681%	$237.856	$237.86	$237.85	$237.90
Purchase #6	$82.99	8.677%	$90.191	$90.19	$90.20	$90.20
Purchase #7	$39.31	5.657%	$41.5338	$41.53	$41.55	$41.50
7 purchase totals =	$719.58		$768.9420	$768.94	$768.95	$769.00