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	$228.45	13.868%	$260.1314	$260.13	$260.15	$260.10
Purchase #2	$207.68	13.700%	$236.1322	$236.13	$236.15	$236.10
Purchase #3	$62.69	13.672%	$71.261	$71.26	$71.25	$71.30
Purchase #4	$129.62	3.693%	$134.4069	$134.41	$134.40	$134.40
Purchase #5	$239.83	6.340%	$255.0352	$255.04	$255.05	$255.00
Purchase #6	$107.28	12.150%	$120.3145	$120.31	$120.30	$120.30
Purchase #7	$182.55	7.400%	$196.0587	$196.06	$196.05	$196.10
7 purchase totals =	$1,158.10		$1,273.3399	$1,273.34	$1,273.35	$1,273.30