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	$9.45	6.720%	$10.085	$10.09	$10.10	$10.10
Purchase #2	$27.32	5.443%	$28.807	$28.81	$28.80	$28.80
Purchase #3	$64.33	11.554%	$71.7627	$71.76	$71.75	$71.80
Purchase #4	$34.79	9.874%	$38.2252	$38.23	$38.25	$38.20
Purchase #5	$35.85	4.268%	$37.3801	$37.38	$37.40	$37.40
Purchase #6	$115.32	8.807%	$125.4762	$125.48	$125.50	$125.50
Purchase #7	$78.56	3.215%	$81.0857	$81.09	$81.10	$81.10
7 purchase totals =	$365.62		$392.8219	$392.84	$392.90	$392.90