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	$77.62	6.172%	$82.4107	$82.41	$82.40	$82.40
Purchase #2	$85.89	4.811%	$90.0222	$90.02	$90.00	$90.00
Purchase #3	$144.44	13.594%	$164.0752	$164.08	$164.10	$164.10
Purchase #4	$184.29	11.687%	$205.828	$205.83	$205.85	$205.80
Purchase #5	$102.27	11.388%	$113.9165	$113.92	$113.90	$113.90
Purchase #6	$103.61	6.317%	$110.155	$110.16	$110.15	$110.20
Purchase #7	$104.48	4.630%	$109.3174	$109.32	$109.30	$109.30
7 purchase totals =	$802.60		$875.7250	$875.74	$875.70	$875.70