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	$173.35	6.873%	$185.2643	$185.26	$185.25	$185.30
Purchase #2	$122.79	7.199%	$131.6297	$131.63	$131.65	$131.60
Purchase #3	$204.53	3.611%	$211.9156	$211.92	$211.90	$211.90
Purchase #4	$220.48	8.277%	$238.7291	$238.73	$238.75	$238.70
Purchase #5	$132.61	10.513%	$146.5513	$146.55	$146.55	$146.60
Purchase #6	$151.55	8.269%	$164.0817	$164.08	$164.10	$164.10
Purchase #7	$188.83	4.156%	$196.6778	$196.68	$196.70	$196.70
7 purchase totals =	$1,194.14		$1,274.8495	$1,274.85	$1,274.90	$1,274.90