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	$239.34	5.751%	$253.1044	$253.10	$253.10	$253.10
Purchase #2	$102.74	8.192%	$111.1565	$111.16	$111.15	$111.20
Purchase #3	$56.32	12.256%	$63.2226	$63.22	$63.20	$63.20
Purchase #4	$191.45	12.469%	$215.3219	$215.32	$215.30	$215.30
Purchase #5	$207.26	6.866%	$221.4905	$221.49	$221.50	$221.50
Purchase #6	$11.98	4.562%	$12.5265	$12.53	$12.55	$12.50
Purchase #7	$162.50	9.576%	$178.061	$178.06	$178.05	$178.10
7 purchase totals =	$971.59		$1,054.8834	$1,054.88	$1,054.85	$1,054.90