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	$34.82	9.529%	$38.138	$38.14	$38.15	$38.10
Purchase #2	$71.93	8.781%	$78.2462	$78.25	$78.25	$78.20
Purchase #3	$89.40	8.234%	$96.7612	$96.76	$96.75	$96.80
Purchase #4	$250.83	6.320%	$266.6825	$266.68	$266.70	$266.70
Purchase #5	$160.27	6.830%	$171.2164	$171.22	$171.20	$171.20
Purchase #6	$175.52	13.855%	$199.8383	$199.84	$199.85	$199.80
Purchase #7	$232.73	9.585%	$255.0372	$255.04	$255.05	$255.00
7 purchase totals =	$1,015.50		$1,105.9198	$1,105.93	$1,105.95	$1,105.80