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	$145.47	4.443%	$151.9332	$151.93	$151.95	$151.90
Purchase #2	$161.90	9.665%	$177.5476	$177.55	$177.55	$177.50
Purchase #3	$101.84	7.360%	$109.3354	$109.34	$109.35	$109.30
Purchase #4	$77.70	9.845%	$85.3496	$85.35	$85.35	$85.30
Purchase #5	$28.68	9.196%	$31.3174	$31.32	$31.30	$31.30
Purchase #6	$79.49	4.605%	$83.1505	$83.15	$83.15	$83.20
Purchase #7	$79.79	13.389%	$90.4731	$90.47	$90.45	$90.50
7 purchase totals =	$674.87		$729.1068	$729.11	$729.10	$729.00