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	$93.26	7.766%	$100.5026	$100.50	$100.50	$100.50
Purchase #2	$161.62	6.170%	$171.592	$171.59	$171.60	$171.60
Purchase #3	$153.88	7.581%	$165.5456	$165.55	$165.55	$165.50
Purchase #4	$13.51	4.856%	$14.166	$14.17	$14.15	$14.20
Purchase #5	$96.63	7.312%	$103.6956	$103.70	$103.70	$103.70
Purchase #6	$156.54	6.831%	$167.2332	$167.23	$167.25	$167.20
Purchase #7	$153.27	12.375%	$172.2372	$172.24	$172.25	$172.20
7 purchase totals =	$828.71		$894.9722	$894.98	$895.00	$894.90