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	$118.78	3.123%	$122.4895	$122.49	$122.50	$122.50
Purchase #2	$169.56	6.535%	$180.6407	$180.64	$180.65	$180.60
Purchase #3	$211.32	5.438%	$222.8116	$222.81	$222.80	$222.80
Purchase #4	$127.77	13.801%	$145.4035	$145.40	$145.40	$145.40
Purchase #5	$112.54	5.183%	$118.3729	$118.37	$118.35	$118.40
Purchase #6	$160.38	11.679%	$179.1108	$179.11	$179.10	$179.10
Purchase #7	$202.48	13.356%	$229.5232	$229.52	$229.50	$229.50
7 purchase totals =	$1,102.83		$1,198.3522	$1,198.34	$1,198.30	$1,198.30