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	$68.85	6.863%	$73.5752	$73.58	$73.60	$73.60
Purchase #2	$218.55	6.796%	$233.4027	$233.40	$233.40	$233.40
Purchase #3	$68.79	11.780%	$76.8935	$76.89	$76.90	$76.90
Purchase #4	$210.83	3.522%	$218.2554	$218.26	$218.25	$218.30
Purchase #5	$111.67	10.388%	$123.2703	$123.27	$123.25	$123.30
Purchase #6	$86.69	7.751%	$93.4093	$93.41	$93.40	$93.40
Purchase #7	$167.31	10.367%	$184.655	$184.66	$184.65	$184.70
7 purchase totals =	$932.69		$1,003.4614	$1,003.47	$1,003.45	$1,003.60