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	$148.62	6.497%	$158.2758	$158.28	$158.30	$158.30
Purchase #2	$147.92	13.473%	$167.8493	$167.85	$167.85	$167.80
Purchase #3	$68.25	5.701%	$72.1409	$72.14	$72.15	$72.10
Purchase #4	$73.58	13.481%	$83.4993	$83.50	$83.50	$83.50
Purchase #5	$143.61	5.208%	$151.0892	$151.09	$151.10	$151.10
Purchase #6	$185.29	6.704%	$197.7118	$197.71	$197.70	$197.70
Purchase #7	$169.49	7.334%	$181.9204	$181.92	$181.90	$181.90
7 purchase totals =	$936.76		$1,012.4867	$1,012.49	$1,012.50	$1,012.40