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	$103.72	8.844%	$112.893	$112.89	$112.90	$112.90
Purchase #2	$35.88	7.489%	$38.5671	$38.57	$38.55	$38.60
Purchase #3	$153.68	7.347%	$164.9709	$164.97	$164.95	$165.00
Purchase #4	$68.69	10.850%	$76.1429	$76.14	$76.15	$76.10
Purchase #5	$141.89	13.559%	$161.1289	$161.13	$161.15	$161.10
Purchase #6	$63.72	5.572%	$67.2705	$67.27	$67.25	$67.30
Purchase #7	$58.75	4.197%	$61.2157	$61.22	$61.20	$61.20
7 purchase totals =	$626.33		$682.1890	$682.19	$682.15	$682.20