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	$30.50	5.283%	$32.1113	$32.11	$32.10	$32.10
Purchase #2	$17.93	5.407%	$18.8995	$18.90	$18.90	$18.90
Purchase #3	$167.80	6.246%	$178.2808	$178.28	$178.30	$178.30
Purchase #4	$94.75	6.445%	$100.8566	$100.86	$100.85	$100.90
Purchase #5	$98.31	4.757%	$102.9866	$102.99	$103.00	$103.00
Purchase #6	$107.46	11.775%	$120.1134	$120.11	$120.10	$120.10
Purchase #7	$107.92	5.650%	$114.0175	$114.02	$114.00	$114.00
7 purchase totals =	$624.67		$667.2657	$667.27	$667.25	$667.30