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	$118.81	8.521%	$128.9338	$128.93	$128.95	$128.90
Purchase #2	$198.90	10.344%	$219.4742	$219.47	$219.45	$219.50
Purchase #3	$66.92	3.518%	$69.2742	$69.27	$69.25	$69.30
Purchase #4	$53.56	12.614%	$60.3161	$60.32	$60.30	$60.30
Purchase #5	$224.31	12.300%	$251.9001	$251.90	$251.90	$251.90
Purchase #6	$137.96	9.846%	$151.5435	$151.54	$151.55	$151.50
Purchase #7	$210.71	13.240%	$238.608	$238.61	$238.60	$238.60
7 purchase totals =	$1,011.17		$1,120.0499	$1,120.04	$1,120.00	$1,120.00