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	$143.86	7.855%	$155.1602	$155.16	$155.15	$155.20
Purchase #2	$223.62	6.782%	$238.7859	$238.79	$238.80	$238.80
Purchase #3	$196.70	7.579%	$211.6079	$211.61	$211.60	$211.60
Purchase #4	$226.94	10.605%	$251.007	$251.01	$251.00	$251.00
Purchase #5	$174.68	12.506%	$196.5255	$196.53	$196.55	$196.50
Purchase #6	$119.88	6.145%	$127.2466	$127.25	$127.25	$127.20
Purchase #7	$57.81	5.683%	$61.0953	$61.10	$61.10	$61.10
7 purchase totals =	$1,143.49		$1,241.4284	$1,241.45	$1,241.45	$1,241.40