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	$170.51	7.155%	$182.71	$182.71	$182.70	$182.70
Purchase #2	$242.33	8.284%	$262.4046	$262.40	$262.40	$262.40
Purchase #3	$123.63	3.127%	$127.4959	$127.50	$127.50	$127.50
Purchase #4	$193.38	3.635%	$200.4094	$200.41	$200.40	$200.40
Purchase #5	$31.47	5.180%	$33.1001	$33.10	$33.10	$33.10
Purchase #6	$125.60	9.156%	$137.0999	$137.10	$137.10	$137.10
Purchase #7	$247.31	9.824%	$271.6057	$271.61	$271.60	$271.60
7 purchase totals =	$1,134.23		$1,214.8256	$1,214.83	$1,214.80	$1,214.80