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	$88.70	12.230%	$99.548	$99.55	$99.55	$99.50
Purchase #2	$239.25	3.318%	$247.1883	$247.19	$247.20	$247.20
Purchase #3	$105.31	3.220%	$108.701	$108.70	$108.70	$108.70
Purchase #4	$220.89	12.699%	$248.9408	$248.94	$248.95	$248.90
Purchase #5	$225.90	3.283%	$233.3163	$233.32	$233.30	$233.30
Purchase #6	$88.56	9.468%	$96.9449	$96.94	$96.95	$96.90
Purchase #7	$57.31	12.699%	$64.5878	$64.59	$64.60	$64.60
7 purchase totals =	$1,025.92		$1,099.2271	$1,099.23	$1,099.25	$1,099.10