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	$218.93	8.648%	$237.8631	$237.86	$237.85	$237.90
Purchase #2	$25.27	8.673%	$27.4617	$27.46	$27.45	$27.50
Purchase #3	$141.77	11.751%	$158.4294	$158.43	$158.45	$158.40
Purchase #4	$247.85	3.384%	$256.2372	$256.24	$256.25	$256.20
Purchase #5	$203.59	5.847%	$215.4939	$215.49	$215.50	$215.50
Purchase #6	$96.26	3.260%	$99.3981	$99.40	$99.40	$99.40
Purchase #7	$247.38	12.529%	$278.3742	$278.37	$278.35	$278.40
7 purchase totals =	$1,181.05		$1,273.2576	$1,273.25	$1,273.25	$1,273.30