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	$65.88	10.466%	$72.775	$72.78	$72.80	$72.80
Purchase #2	$96.39	6.147%	$102.3151	$102.32	$102.30	$102.30
Purchase #3	$149.37	11.760%	$166.9359	$166.94	$166.95	$166.90
Purchase #4	$167.56	6.304%	$178.123	$178.12	$178.10	$178.10
Purchase #5	$92.66	11.320%	$103.1491	$103.15	$103.15	$103.10
Purchase #6	$209.88	9.768%	$230.3811	$230.38	$230.40	$230.40
Purchase #7	$218.89	8.597%	$237.708	$237.71	$237.70	$237.70
7 purchase totals =	$1,000.63		$1,091.3872	$1,091.40	$1,091.40	$1,091.30