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	$82.73	11.192%	$91.9891	$91.99	$92.00	$92.00
Purchase #2	$71.37	7.510%	$76.7299	$76.73	$76.75	$76.70
Purchase #3	$243.73	11.375%	$271.4543	$271.45	$271.45	$271.50
Purchase #4	$249.61	4.712%	$261.3716	$261.37	$261.35	$261.40
Purchase #5	$121.86	13.675%	$138.5244	$138.52	$138.50	$138.50
Purchase #6	$38.51	5.424%	$40.5988	$40.60	$40.60	$40.60
Purchase #7	$125.73	6.850%	$134.3425	$134.34	$134.35	$134.30
7 purchase totals =	$933.54		$1,015.0106	$1,015.00	$1,015.00	$1,015.00