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	$62.72	13.825%	$71.391	$71.39	$71.40	$71.40
Purchase #2	$148.41	6.132%	$157.5105	$157.51	$157.50	$157.50
Purchase #3	$102.91	6.143%	$109.2318	$109.23	$109.25	$109.20
Purchase #4	$230.59	5.747%	$243.842	$243.84	$243.85	$243.80
Purchase #5	$7.42	6.351%	$7.8912	$7.89	$7.90	$7.90
Purchase #6	$248.38	5.558%	$262.185	$262.19	$262.20	$262.20
Purchase #7	$14.32	9.229%	$15.6416	$15.64	$15.65	$15.60
7 purchase totals =	$814.75		$867.6931	$867.69	$867.75	$867.60