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	$105.92	3.265%	$109.3783	$109.38	$109.40	$109.40
Purchase #2	$222.95	13.274%	$252.5444	$252.54	$252.55	$252.50
Purchase #3	$40.83	7.451%	$43.8722	$43.87	$43.85	$43.90
Purchase #4	$113.29	4.167%	$118.0108	$118.01	$118.00	$118.00
Purchase #5	$248.53	3.118%	$256.2792	$256.28	$256.30	$256.30
Purchase #6	$234.48	12.279%	$263.2718	$263.27	$263.25	$263.30
Purchase #7	$160.79	11.260%	$178.895	$178.90	$178.90	$178.90
7 purchase totals =	$1,126.79		$1,222.2517	$1,222.25	$1,222.25	$1,222.30