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	$87.84	7.443%	$94.3779	$94.38	$94.40	$94.40
Purchase #2	$102.69	11.645%	$114.6483	$114.65	$114.65	$114.60
Purchase #3	$84.42	6.410%	$89.8313	$89.83	$89.85	$89.80
Purchase #4	$187.72	9.693%	$205.9157	$205.92	$205.90	$205.90
Purchase #5	$80.41	9.173%	$87.786	$87.79	$87.80	$87.80
Purchase #6	$245.49	13.817%	$279.4094	$279.41	$279.40	$279.40
Purchase #7	$128.30	6.523%	$136.669	$136.67	$136.65	$136.70
7 purchase totals =	$916.87		$1,008.6376	$1,008.65	$1,008.65	$1,008.60