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	$98.39	7.552%	$105.8204	$105.82	$105.80	$105.80
Purchase #2	$88.51	11.597%	$98.7745	$98.77	$98.75	$98.80
Purchase #3	$80.68	10.265%	$88.9618	$88.96	$88.95	$89.00
Purchase #4	$177.98	10.781%	$197.168	$197.17	$197.15	$197.20
Purchase #5	$162.33	12.316%	$182.3226	$182.32	$182.30	$182.30
Purchase #6	$200.52	4.162%	$208.8656	$208.87	$208.85	$208.90
Purchase #7	$64.41	10.269%	$71.0243	$71.02	$71.00	$71.00
7 purchase totals =	$872.82		$952.9372	$952.93	$952.80	$953.00