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	$182.41	7.622%	$196.3133	$196.31	$196.30	$196.30
Purchase #2	$85.96	6.372%	$91.4374	$91.44	$91.45	$91.40
Purchase #3	$196.67	10.866%	$218.0402	$218.04	$218.05	$218.00
Purchase #4	$9.44	13.294%	$10.695	$10.70	$10.70	$10.70
Purchase #5	$164.30	13.506%	$186.4904	$186.49	$186.50	$186.50
Purchase #6	$249.53	13.705%	$283.7281	$283.73	$283.75	$283.70
Purchase #7	$125.62	8.748%	$136.6092	$136.61	$136.60	$136.60
7 purchase totals =	$1,013.93		$1,123.3136	$1,123.32	$1,123.35	$1,123.20