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	$133.87	12.465%	$150.5569	$150.56	$150.55	$150.60
Purchase #2	$215.40	12.671%	$242.6933	$242.69	$242.70	$242.70
Purchase #3	$160.66	9.680%	$176.2119	$176.21	$176.20	$176.20
Purchase #4	$178.69	11.313%	$198.9052	$198.91	$198.90	$198.90
Purchase #5	$177.39	7.532%	$190.751	$190.75	$190.75	$190.80
Purchase #6	$156.94	4.670%	$164.2691	$164.27	$164.25	$164.30
Purchase #7	$58.72	5.477%	$61.9361	$61.94	$61.95	$61.90
7 purchase totals =	$1,081.67		$1,185.3235	$1,185.33	$1,185.30	$1,185.40