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	$96.52	13.211%	$109.2713	$109.27	$109.25	$109.30
Purchase #2	$209.69	5.176%	$220.5436	$220.54	$220.55	$220.50
Purchase #3	$75.39	4.173%	$78.536	$78.54	$78.55	$78.50
Purchase #4	$161.54	7.297%	$173.3276	$173.33	$173.35	$173.30
Purchase #5	$134.57	12.815%	$151.8151	$151.82	$151.80	$151.80
Purchase #6	$155.88	7.836%	$168.0948	$168.09	$168.10	$168.10
Purchase #7	$182.52	7.757%	$196.6781	$196.68	$196.70	$196.70
7 purchase totals =	$1,016.11		$1,098.2665	$1,098.27	$1,098.30	$1,098.20