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	$134.86	8.209%	$145.9307	$145.93	$145.95	$145.90
Purchase #2	$35.56	11.209%	$39.5459	$39.55	$39.55	$39.50
Purchase #3	$119.49	6.119%	$126.8016	$126.80	$126.80	$126.80
Purchase #4	$123.42	9.234%	$134.8166	$134.82	$134.80	$134.80
Purchase #5	$119.52	6.573%	$127.376	$127.38	$127.40	$127.40
Purchase #6	$244.40	8.373%	$264.8636	$264.86	$264.85	$264.90
Purchase #7	$217.93	5.197%	$229.2558	$229.26	$229.25	$229.30
7 purchase totals =	$995.18		$1,068.5902	$1,068.60	$1,068.60	$1,068.60