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	$173.32	6.866%	$185.2202	$185.22	$185.20	$185.20
Purchase #2	$152.59	4.516%	$159.481	$159.48	$159.50	$159.50
Purchase #3	$78.59	9.830%	$86.3154	$86.32	$86.30	$86.30
Purchase #4	$94.39	4.462%	$98.6017	$98.60	$98.60	$98.60
Purchase #5	$34.30	4.578%	$35.8703	$35.87	$35.85	$35.90
Purchase #6	$38.45	8.465%	$41.7048	$41.70	$41.70	$41.70
Purchase #7	$137.75	5.566%	$145.4172	$145.42	$145.40	$145.40
7 purchase totals =	$709.39		$752.6106	$752.61	$752.55	$752.60