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	$167.53	6.761%	$178.8567	$178.86	$178.85	$178.90
Purchase #2	$39.33	4.647%	$41.1577	$41.16	$41.15	$41.20
Purchase #3	$170.48	6.714%	$181.926	$181.93	$181.95	$181.90
Purchase #4	$213.66	8.421%	$231.6523	$231.65	$231.65	$231.70
Purchase #5	$153.78	10.447%	$169.8454	$169.85	$169.85	$169.80
Purchase #6	$133.58	4.404%	$139.4629	$139.46	$139.45	$139.50
Purchase #7	$214.44	4.264%	$223.5837	$223.58	$223.60	$223.60
7 purchase totals =	$1,092.80		$1,166.4847	$1,166.49	$1,166.50	$1,166.60