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	$98.54	11.505%	$109.877	$109.88	$109.90	$109.90
Purchase #2	$94.76	4.824%	$99.3312	$99.33	$99.35	$99.30
Purchase #3	$196.78	6.215%	$209.0099	$209.01	$209.00	$209.00
Purchase #4	$92.63	11.573%	$103.3501	$103.35	$103.35	$103.40
Purchase #5	$114.50	5.167%	$120.4162	$120.42	$120.40	$120.40
Purchase #6	$220.75	8.223%	$238.9023	$238.90	$238.90	$238.90
Purchase #7	$131.49	10.273%	$144.998	$145.00	$145.00	$145.00
7 purchase totals =	$949.45		$1,025.8847	$1,025.89	$1,025.90	$1,025.90