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	$188.87	13.768%	$214.8736	$214.87	$214.85	$214.90
Purchase #2	$229.90	4.440%	$240.1076	$240.11	$240.10	$240.10
Purchase #3	$109.29	9.429%	$119.595	$119.60	$119.60	$119.60
Purchase #4	$143.65	7.124%	$153.8836	$153.88	$153.90	$153.90
Purchase #5	$210.57	4.599%	$220.2541	$220.25	$220.25	$220.30
Purchase #6	$60.55	11.372%	$67.4357	$67.44	$67.45	$67.40
Purchase #7	$73.47	12.772%	$82.8536	$82.85	$82.85	$82.90
7 purchase totals =	$1,016.30		$1,099.0032	$1,099.00	$1,099.00	$1,099.10