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	$106.54	7.379%	$114.4016	$114.40	$114.40	$114.40
Purchase #2	$138.36	13.112%	$156.5018	$156.50	$156.50	$156.50
Purchase #3	$92.85	13.367%	$105.2613	$105.26	$105.25	$105.30
Purchase #4	$98.48	6.541%	$104.9216	$104.92	$104.90	$104.90
Purchase #5	$96.93	3.401%	$100.2266	$100.23	$100.25	$100.20
Purchase #6	$198.60	13.802%	$226.0108	$226.01	$226.00	$226.00
Purchase #7	$192.92	9.265%	$210.794	$210.79	$210.80	$210.80
7 purchase totals =	$924.68		$1,018.1177	$1,018.11	$1,018.10	$1,018.10