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	$90.58	11.399%	$100.9052	$100.91	$100.90	$100.90
Purchase #2	$169.89	7.229%	$182.1713	$182.17	$182.15	$182.20
Purchase #3	$232.36	12.410%	$261.1959	$261.20	$261.20	$261.20
Purchase #4	$87.42	3.618%	$90.5829	$90.58	$90.60	$90.60
Purchase #5	$227.59	9.226%	$248.5875	$248.59	$248.60	$248.60
Purchase #6	$54.46	4.271%	$56.786	$56.79	$56.80	$56.80
Purchase #7	$155.72	3.259%	$160.7949	$160.79	$160.80	$160.80
7 purchase totals =	$1,018.02		$1,101.0237	$1,101.03	$1,101.05	$1,101.10