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	$95.25	3.379%	$98.4685	$98.47	$98.45	$98.50
Purchase #2	$98.70	4.870%	$103.5067	$103.51	$103.50	$103.50
Purchase #3	$168.94	13.281%	$191.3769	$191.38	$191.40	$191.40
Purchase #4	$23.69	3.407%	$24.4971	$24.50	$24.50	$24.50
Purchase #5	$218.77	12.780%	$246.7288	$246.73	$246.75	$246.70
Purchase #6	$39.87	4.727%	$41.7547	$41.75	$41.75	$41.80
Purchase #7	$73.42	12.368%	$82.5006	$82.50	$82.50	$82.50
7 purchase totals =	$718.64		$788.8333	$788.84	$788.85	$788.90