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	$186.38	10.500%	$205.9499	$205.95	$205.95	$205.90
Purchase #2	$49.83	7.708%	$53.6709	$53.67	$53.65	$53.70
Purchase #3	$78.87	8.739%	$85.7624	$85.76	$85.75	$85.80
Purchase #4	$166.38	13.465%	$188.7831	$188.78	$188.80	$188.80
Purchase #5	$49.34	9.730%	$54.1408	$54.14	$54.15	$54.10
Purchase #6	$7.33	6.712%	$7.822	$7.82	$7.80	$7.80
Purchase #7	$230.56	11.855%	$257.8929	$257.89	$257.90	$257.90
7 purchase totals =	$768.69		$854.0220	$854.01	$854.00	$854.00