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	$158.94	13.702%	$180.718	$180.72	$180.70	$180.70
Purchase #2	$180.75	13.423%	$205.0121	$205.01	$205.00	$205.00
Purchase #3	$215.50	6.306%	$229.0894	$229.09	$229.10	$229.10
Purchase #4	$133.34	6.828%	$142.4445	$142.44	$142.45	$142.40
Purchase #5	$127.85	7.392%	$137.3007	$137.30	$137.30	$137.30
Purchase #6	$95.36	8.327%	$103.3006	$103.30	$103.30	$103.30
Purchase #7	$49.51	8.709%	$53.8218	$53.82	$53.80	$53.80
7 purchase totals =	$961.25		$1,051.6871	$1,051.68	$1,051.65	$1,051.60