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	$238.59	4.820%	$250.09	$250.09	$250.10	$250.10
Purchase #2	$86.92	12.373%	$97.6746	$97.67	$97.65	$97.70
Purchase #3	$138.76	6.363%	$147.5893	$147.59	$147.60	$147.60
Purchase #4	$211.44	3.376%	$218.5782	$218.58	$218.60	$218.60
Purchase #5	$237.63	3.214%	$245.2674	$245.27	$245.25	$245.30
Purchase #6	$103.87	7.166%	$111.3133	$111.31	$111.30	$111.30
Purchase #7	$222.70	13.109%	$251.8937	$251.89	$251.90	$251.90
7 purchase totals =	$1,239.91		$1,322.4065	$1,322.40	$1,322.40	$1,322.50