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	$92.26	6.843%	$98.5734	$98.57	$98.55	$98.60
Purchase #2	$144.30	11.147%	$160.3851	$160.39	$160.40	$160.40
Purchase #3	$147.31	10.215%	$162.3577	$162.36	$162.35	$162.40
Purchase #4	$63.51	13.362%	$71.9962	$72.00	$72.00	$72.00
Purchase #5	$218.89	4.795%	$229.3858	$229.39	$229.40	$229.40
Purchase #6	$74.25	5.369%	$78.2365	$78.24	$78.25	$78.20
Purchase #7	$11.58	11.152%	$12.8714	$12.87	$12.85	$12.90
7 purchase totals =	$752.10		$813.8061	$813.82	$813.80	$813.90