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	$69.75	12.269%	$78.3076	$78.31	$78.30	$78.30
Purchase #2	$213.83	13.123%	$241.8909	$241.89	$241.90	$241.90
Purchase #3	$83.49	9.616%	$91.5184	$91.52	$91.50	$91.50
Purchase #4	$228.85	4.581%	$239.3336	$239.33	$239.35	$239.30
Purchase #5	$73.52	7.263%	$78.8598	$78.86	$78.85	$78.90
Purchase #6	$216.55	10.819%	$239.9785	$239.98	$240.00	$240.00
Purchase #7	$82.68	11.269%	$91.9972	$92.00	$92.00	$92.00
7 purchase totals =	$968.67		$1,061.8860	$1,061.89	$1,061.90	$1,061.90