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	$100.63	10.404%	$111.0995	$111.10	$111.10	$111.10
Purchase #2	$208.95	10.807%	$231.5312	$231.53	$231.55	$231.50
Purchase #3	$139.89	4.192%	$145.7542	$145.75	$145.75	$145.80
Purchase #4	$14.29	13.720%	$16.2506	$16.25	$16.25	$16.30
Purchase #5	$107.50	6.645%	$114.6434	$114.64	$114.65	$114.60
Purchase #6	$26.74	10.346%	$29.5065	$29.51	$29.50	$29.50
Purchase #7	$104.83	5.501%	$110.5967	$110.60	$110.60	$110.60
7 purchase totals =	$702.83		$759.3821	$759.38	$759.40	$759.40