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	$44.58	3.185%	$45.9999	$46.00	$46.00	$46.00
Purchase #2	$237.54	10.346%	$262.1159	$262.12	$262.10	$262.10
Purchase #3	$63.76	11.259%	$70.9387	$70.94	$70.95	$70.90
Purchase #4	$178.82	4.801%	$187.4051	$187.41	$187.40	$187.40
Purchase #5	$223.31	6.805%	$238.5062	$238.51	$238.50	$238.50
Purchase #6	$8.25	7.717%	$8.8867	$8.89	$8.90	$8.90
Purchase #7	$134.63	12.119%	$150.9458	$150.95	$150.95	$150.90
7 purchase totals =	$890.89		$964.7983	$964.82	$964.80	$964.70