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	$51.66	12.788%	$58.2663	$58.27	$58.25	$58.30
Purchase #2	$174.39	13.838%	$198.5221	$198.52	$198.50	$198.50
Purchase #3	$214.77	6.374%	$228.4594	$228.46	$228.45	$228.50
Purchase #4	$158.83	3.772%	$164.8211	$164.82	$164.80	$164.80
Purchase #5	$142.96	10.632%	$158.1595	$158.16	$158.15	$158.20
Purchase #6	$28.86	7.522%	$31.0308	$31.03	$31.05	$31.00
Purchase #7	$31.76	11.220%	$35.3235	$35.32	$35.30	$35.30
7 purchase totals =	$803.23		$874.5827	$874.58	$874.50	$874.60