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	$233.86	9.306%	$255.623	$255.62	$255.60	$255.60
Purchase #2	$155.93	5.382%	$164.3222	$164.32	$164.30	$164.30
Purchase #3	$35.78	5.477%	$37.7397	$37.74	$37.75	$37.70
Purchase #4	$196.37	11.533%	$219.0174	$219.02	$219.00	$219.00
Purchase #5	$198.98	6.362%	$211.6391	$211.64	$211.65	$211.60
Purchase #6	$6.93	6.658%	$7.3914	$7.39	$7.40	$7.40
Purchase #7	$237.28	13.304%	$268.8477	$268.85	$268.85	$268.80
7 purchase totals =	$1,065.13		$1,164.5805	$1,164.58	$1,164.55	$1,164.40