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	$169.31	7.623%	$182.2165	$182.22	$182.20	$182.20
Purchase #2	$118.33	7.745%	$127.4947	$127.49	$127.50	$127.50
Purchase #3	$84.83	6.350%	$90.2167	$90.22	$90.20	$90.20
Purchase #4	$87.59	3.411%	$90.5777	$90.58	$90.60	$90.60
Purchase #5	$181.36	12.434%	$203.9103	$203.91	$203.90	$203.90
Purchase #6	$68.54	10.605%	$75.8087	$75.81	$75.80	$75.80
Purchase #7	$113.85	12.773%	$128.3921	$128.39	$128.40	$128.40
7 purchase totals =	$823.81		$898.6167	$898.62	$898.60	$898.60