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	$55.25	8.395%	$59.8882	$59.89	$59.90	$59.90
Purchase #2	$174.39	3.842%	$181.0901	$181.09	$181.10	$181.10
Purchase #3	$180.65	13.559%	$205.1443	$205.14	$205.15	$205.10
Purchase #4	$140.78	10.571%	$155.6619	$155.66	$155.65	$155.70
Purchase #5	$153.73	11.377%	$171.2199	$171.22	$171.20	$171.20
Purchase #6	$98.72	4.614%	$103.2749	$103.27	$103.25	$103.30
Purchase #7	$183.43	8.477%	$198.9794	$198.98	$199.00	$199.00
7 purchase totals =	$986.95		$1,075.2587	$1,075.25	$1,075.25	$1,075.30