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	$98.53	7.436%	$105.8567	$105.86	$105.85	$105.90
Purchase #2	$218.95	12.579%	$246.4917	$246.49	$246.50	$246.50
Purchase #3	$158.56	12.559%	$178.4736	$178.47	$178.45	$178.50
Purchase #4	$242.77	5.567%	$256.285	$256.29	$256.30	$256.30
Purchase #5	$156.43	5.854%	$165.5874	$165.59	$165.60	$165.60
Purchase #6	$7.51	7.806%	$8.0962	$8.10	$8.10	$8.10
Purchase #7	$101.92	7.627%	$109.6934	$109.69	$109.70	$109.70
7 purchase totals =	$984.67		$1,070.4840	$1,070.49	$1,070.50	$1,070.60