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	$191.85	13.141%	$217.061	$217.06	$217.05	$217.10
Purchase #2	$138.54	8.613%	$150.4725	$150.47	$150.45	$150.50
Purchase #3	$196.44	8.789%	$213.7051	$213.71	$213.70	$213.70
Purchase #4	$108.94	8.864%	$118.5964	$118.60	$118.60	$118.60
Purchase #5	$238.34	3.319%	$246.2505	$246.25	$246.25	$246.30
Purchase #6	$173.66	13.364%	$196.8679	$196.87	$196.85	$196.90
Purchase #7	$157.74	8.612%	$171.3246	$171.32	$171.30	$171.30
7 purchase totals =	$1,205.51		$1,314.2780	$1,314.28	$1,314.20	$1,314.40