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	$127.88	9.778%	$140.3841	$140.38	$140.40	$140.40
Purchase #2	$74.39	6.716%	$79.386	$79.39	$79.40	$79.40
Purchase #3	$187.86	4.754%	$196.7909	$196.79	$196.80	$196.80
Purchase #4	$163.78	3.122%	$168.8932	$168.89	$168.90	$168.90
Purchase #5	$163.56	5.371%	$172.3448	$172.34	$172.35	$172.30
Purchase #6	$103.54	6.362%	$110.1272	$110.13	$110.15	$110.10
Purchase #7	$156.29	6.848%	$166.9927	$166.99	$167.00	$167.00
7 purchase totals =	$977.30		$1,034.9189	$1,034.91	$1,035.00	$1,034.90