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	$59.89	9.748%	$65.7281	$65.73	$65.75	$65.70
Purchase #2	$93.79	4.646%	$98.1475	$98.15	$98.15	$98.10
Purchase #3	$234.60	6.623%	$250.1376	$250.14	$250.15	$250.10
Purchase #4	$121.79	7.382%	$130.7805	$130.78	$130.80	$130.80
Purchase #5	$233.38	9.274%	$255.0237	$255.02	$255.00	$255.00
Purchase #6	$122.31	4.328%	$127.6036	$127.60	$127.60	$127.60
Purchase #7	$77.59	13.290%	$87.9017	$87.90	$87.90	$87.90
7 purchase totals =	$943.35		$1,015.3227	$1,015.32	$1,015.35	$1,015.20