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	$127.26	3.537%	$131.7612	$131.76	$131.75	$131.80
Purchase #2	$54.59	12.195%	$61.2473	$61.25	$61.25	$61.20
Purchase #3	$200.91	6.310%	$213.5874	$213.59	$213.60	$213.60
Purchase #4	$220.86	9.859%	$242.6346	$242.63	$242.65	$242.60
Purchase #5	$157.83	5.438%	$166.4128	$166.41	$166.40	$166.40
Purchase #6	$71.64	9.735%	$78.6142	$78.61	$78.60	$78.60
Purchase #7	$112.95	9.765%	$123.9796	$123.98	$124.00	$124.00
7 purchase totals =	$946.04		$1,018.2371	$1,018.23	$1,018.25	$1,018.20