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	$206.97	7.193%	$221.8574	$221.86	$221.85	$221.90
Purchase #2	$35.90	6.296%	$38.1603	$38.16	$38.15	$38.20
Purchase #3	$173.55	10.134%	$191.1376	$191.14	$191.15	$191.10
Purchase #4	$168.86	11.416%	$188.1371	$188.14	$188.15	$188.10
Purchase #5	$228.63	4.173%	$238.1707	$238.17	$238.15	$238.20
Purchase #6	$50.35	8.389%	$54.5739	$54.57	$54.55	$54.60
Purchase #7	$168.58	6.420%	$179.4028	$179.40	$179.40	$179.40
7 purchase totals =	$1,032.84		$1,111.4398	$1,111.44	$1,111.40	$1,111.50