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	$226.40	6.604%	$241.3515	$241.35	$241.35	$241.40
Purchase #2	$96.53	6.126%	$102.4434	$102.44	$102.45	$102.40
Purchase #3	$118.74	13.505%	$134.7758	$134.78	$134.80	$134.80
Purchase #4	$159.88	13.535%	$181.5198	$181.52	$181.50	$181.50
Purchase #5	$175.90	3.729%	$182.4593	$182.46	$182.45	$182.50
Purchase #6	$123.58	8.204%	$133.7185	$133.72	$133.70	$133.70
Purchase #7	$74.62	12.381%	$83.8587	$83.86	$83.85	$83.90
7 purchase totals =	$975.65		$1,060.1270	$1,060.13	$1,060.10	$1,060.20