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	$92.99	13.424%	$105.473	$105.47	$105.45	$105.50
Purchase #2	$57.97	11.155%	$64.4366	$64.44	$64.45	$64.40
Purchase #3	$115.78	10.408%	$127.8304	$127.83	$127.85	$127.80
Purchase #4	$153.47	4.397%	$160.2181	$160.22	$160.20	$160.20
Purchase #5	$79.70	11.696%	$89.0217	$89.02	$89.00	$89.00
Purchase #6	$224.40	11.807%	$250.8949	$250.89	$250.90	$250.90
Purchase #7	$146.87	9.736%	$161.1693	$161.17	$161.15	$161.20
7 purchase totals =	$871.18		$959.0440	$959.04	$959.00	$959.00