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	$191.25	6.609%	$203.8897	$203.89	$203.90	$203.90
Purchase #2	$35.26	5.163%	$37.0805	$37.08	$37.10	$37.10
Purchase #3	$33.76	5.227%	$35.5246	$35.52	$35.50	$35.50
Purchase #4	$116.68	6.120%	$123.8208	$123.82	$123.80	$123.80
Purchase #5	$200.38	4.856%	$210.1105	$210.11	$210.10	$210.10
Purchase #6	$73.72	5.314%	$77.6375	$77.64	$77.65	$77.60
Purchase #7	$169.67	10.786%	$187.9706	$187.97	$187.95	$188.00
7 purchase totals =	$820.72		$876.0342	$876.03	$876.00	$876.00