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	$136.37	6.281%	$144.9354	$144.94	$144.95	$144.90
Purchase #2	$92.25	3.499%	$95.4778	$95.48	$95.50	$95.50
Purchase #3	$140.33	11.506%	$156.4764	$156.48	$156.50	$156.50
Purchase #4	$175.78	6.287%	$186.8313	$186.83	$186.85	$186.80
Purchase #5	$137.83	6.121%	$146.2666	$146.27	$146.25	$146.30
Purchase #6	$202.81	11.446%	$226.0236	$226.02	$226.00	$226.00
Purchase #7	$216.52	6.200%	$229.9442	$229.94	$229.95	$229.90
7 purchase totals =	$1,101.89		$1,185.9553	$1,185.96	$1,186.00	$1,185.90