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	$138.82	6.117%	$147.3116	$147.31	$147.30	$147.30
Purchase #2	$240.93	5.462%	$254.0896	$254.09	$254.10	$254.10
Purchase #3	$92.62	4.174%	$96.486	$96.49	$96.50	$96.50
Purchase #4	$170.31	3.342%	$176.0018	$176.00	$176.00	$176.00
Purchase #5	$205.93	13.573%	$233.8809	$233.88	$233.90	$233.90
Purchase #6	$187.53	4.700%	$196.3439	$196.34	$196.35	$196.30
Purchase #7	$93.43	13.358%	$105.9104	$105.91	$105.90	$105.90
7 purchase totals =	$1,129.57		$1,210.0242	$1,210.02	$1,210.05	$1,210.00