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	$168.47	11.866%	$188.4607	$188.46	$188.45	$188.50
Purchase #2	$73.96	3.321%	$76.4162	$76.42	$76.40	$76.40
Purchase #3	$163.57	9.169%	$178.5677	$178.57	$178.55	$178.60
Purchase #4	$147.34	9.420%	$161.2194	$161.22	$161.20	$161.20
Purchase #5	$156.34	4.210%	$162.9219	$162.92	$162.90	$162.90
Purchase #6	$68.69	4.567%	$71.8271	$71.83	$71.85	$71.80
Purchase #7	$96.32	5.791%	$101.8979	$101.90	$101.90	$101.90
7 purchase totals =	$874.69		$941.3109	$941.32	$941.25	$941.30