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	$159.66	5.830%	$168.9682	$168.97	$168.95	$169.00
Purchase #2	$132.47	7.424%	$142.3046	$142.30	$142.30	$142.30
Purchase #3	$214.35	5.840%	$226.868	$226.87	$226.85	$226.90
Purchase #4	$21.82	7.631%	$23.4851	$23.49	$23.50	$23.50
Purchase #5	$137.56	11.851%	$153.8622	$153.86	$153.85	$153.90
Purchase #6	$85.39	3.708%	$88.5563	$88.56	$88.55	$88.60
Purchase #7	$191.28	3.563%	$198.0953	$198.10	$198.10	$198.10
7 purchase totals =	$942.53		$1,002.1397	$1,002.15	$1,002.10	$1,002.30