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	$181.66	3.257%	$187.5767	$187.58	$187.60	$187.60
Purchase #2	$208.81	12.357%	$234.6127	$234.61	$234.60	$234.60
Purchase #3	$65.54	11.165%	$72.8575	$72.86	$72.85	$72.90
Purchase #4	$179.86	12.378%	$202.1231	$202.12	$202.10	$202.10
Purchase #5	$112.64	13.417%	$127.7529	$127.75	$127.75	$127.80
Purchase #6	$94.98	4.709%	$99.4526	$99.45	$99.45	$99.50
Purchase #7	$73.95	5.531%	$78.0402	$78.04	$78.05	$78.00
7 purchase totals =	$917.44		$1,002.4157	$1,002.41	$1,002.40	$1,002.50