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	$127.40	7.303%	$136.704	$136.70	$136.70	$136.70
Purchase #2	$71.35	10.568%	$78.8903	$78.89	$78.90	$78.90
Purchase #3	$211.87	9.399%	$231.7837	$231.78	$231.80	$231.80
Purchase #4	$31.89	3.743%	$33.0836	$33.08	$33.10	$33.10
Purchase #5	$172.52	3.224%	$178.082	$178.08	$178.10	$178.10
Purchase #6	$250.74	5.153%	$263.6606	$263.66	$263.65	$263.70
Purchase #7	$134.49	4.554%	$140.6147	$140.61	$140.60	$140.60
7 purchase totals =	$1,000.26		$1,062.8189	$1,062.80	$1,062.85	$1,062.90