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	$247.86	5.265%	$260.9098	$260.91	$260.90	$260.90
Purchase #2	$189.97	5.443%	$200.3101	$200.31	$200.30	$200.30
Purchase #3	$93.46	12.798%	$105.421	$105.42	$105.40	$105.40
Purchase #4	$157.66	10.502%	$174.2175	$174.22	$174.20	$174.20
Purchase #5	$159.36	13.509%	$180.8879	$180.89	$180.90	$180.90
Purchase #6	$12.51	5.215%	$13.1624	$13.16	$13.15	$13.20
Purchase #7	$117.36	8.669%	$127.5339	$127.53	$127.55	$127.50
7 purchase totals =	$978.18		$1,062.4426	$1,062.44	$1,062.40	$1,062.40