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	$114.68	11.105%	$127.4152	$127.42	$127.40	$127.40
Purchase #2	$237.36	11.191%	$263.923	$263.92	$263.90	$263.90
Purchase #3	$54.54	8.117%	$58.967	$58.97	$58.95	$59.00
Purchase #4	$198.83	3.814%	$206.4134	$206.41	$206.40	$206.40
Purchase #5	$134.87	11.585%	$150.4947	$150.49	$150.50	$150.50
Purchase #6	$95.53	8.436%	$103.5889	$103.59	$103.60	$103.60
Purchase #7	$182.70	11.406%	$203.5388	$203.54	$203.55	$203.50
7 purchase totals =	$1,018.51		$1,114.3410	$1,114.34	$1,114.30	$1,114.30