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	$65.28	9.470%	$71.462	$71.46	$71.45	$71.50
Purchase #2	$165.54	10.325%	$182.632	$182.63	$182.65	$182.60
Purchase #3	$58.89	7.481%	$63.2956	$63.30	$63.30	$63.30
Purchase #4	$235.98	10.132%	$259.8895	$259.89	$259.90	$259.90
Purchase #5	$119.80	3.405%	$123.8792	$123.88	$123.90	$123.90
Purchase #6	$51.82	4.658%	$54.2338	$54.23	$54.25	$54.20
Purchase #7	$191.71	11.565%	$213.8813	$213.88	$213.90	$213.90
7 purchase totals =	$889.02		$969.2734	$969.27	$969.35	$969.30