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	$79.82	11.671%	$89.1358	$89.14	$89.15	$89.10
Purchase #2	$247.42	4.874%	$259.4793	$259.48	$259.50	$259.50
Purchase #3	$22.49	8.156%	$24.3243	$24.32	$24.30	$24.30
Purchase #4	$83.35	3.317%	$86.1147	$86.11	$86.10	$86.10
Purchase #5	$5.26	8.463%	$5.7052	$5.71	$5.70	$5.70
Purchase #6	$152.88	6.403%	$162.6689	$162.67	$162.65	$162.70
Purchase #7	$127.50	9.508%	$139.6227	$139.62	$139.60	$139.60
7 purchase totals =	$718.72		$767.0509	$767.05	$767.00	$767.00