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	$77.92	4.847%	$81.6968	$81.70	$81.70	$81.70
Purchase #2	$209.74	4.325%	$218.8113	$218.81	$218.80	$218.80
Purchase #3	$166.40	12.794%	$187.6892	$187.69	$187.70	$187.70
Purchase #4	$78.31	5.367%	$82.5129	$82.51	$82.50	$82.50
Purchase #5	$203.41	9.588%	$222.913	$222.91	$222.90	$222.90
Purchase #6	$143.86	6.384%	$153.044	$153.04	$153.05	$153.00
Purchase #7	$124.87	4.366%	$130.3218	$130.32	$130.30	$130.30
7 purchase totals =	$1,004.51		$1,076.9890	$1,076.98	$1,076.95	$1,076.90