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	$116.71	9.400%	$127.6807	$127.68	$127.70	$127.70
Purchase #2	$241.39	11.597%	$269.384	$269.38	$269.40	$269.40
Purchase #3	$70.90	7.566%	$76.2643	$76.26	$76.25	$76.30
Purchase #4	$215.93	9.419%	$236.2684	$236.27	$236.25	$236.30
Purchase #5	$111.97	13.627%	$127.2282	$127.23	$127.25	$127.20
Purchase #6	$209.63	4.676%	$219.4323	$219.43	$219.45	$219.40
Purchase #7	$215.58	13.495%	$244.6725	$244.67	$244.65	$244.70
7 purchase totals =	$1,182.11		$1,300.9304	$1,300.92	$1,300.95	$1,301.00