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	$161.59	3.686%	$167.5462	$167.55	$167.55	$167.50
Purchase #2	$35.44	7.215%	$37.997	$38.00	$38.00	$38.00
Purchase #3	$48.45	13.361%	$54.9234	$54.92	$54.90	$54.90
Purchase #4	$120.52	8.291%	$130.5123	$130.51	$130.50	$130.50
Purchase #5	$111.33	6.275%	$118.316	$118.32	$118.30	$118.30
Purchase #6	$124.82	3.249%	$128.8754	$128.88	$128.90	$128.90
Purchase #7	$45.32	8.690%	$49.2583	$49.26	$49.25	$49.30
7 purchase totals =	$647.47		$687.4286	$687.44	$687.40	$687.40