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	$12.50	13.320%	$14.165	$14.17	$14.15	$14.20
Purchase #2	$13.37	3.507%	$13.8389	$13.84	$13.85	$13.80
Purchase #3	$66.37	9.432%	$72.63	$72.63	$72.65	$72.60
Purchase #4	$172.86	6.632%	$184.3241	$184.32	$184.30	$184.30
Purchase #5	$144.55	12.728%	$162.9483	$162.95	$162.95	$162.90
Purchase #6	$19.36	11.604%	$21.6065	$21.61	$21.60	$21.60
Purchase #7	$181.64	8.499%	$197.0776	$197.08	$197.10	$197.10
7 purchase totals =	$610.65		$666.5904	$666.60	$666.60	$666.50