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	$42.73	8.275%	$46.2659	$46.27	$46.25	$46.30
Purchase #2	$36.69	4.744%	$38.4306	$38.43	$38.45	$38.40
Purchase #3	$210.38	5.109%	$221.1283	$221.13	$221.15	$221.10
Purchase #4	$11.63	13.264%	$13.1726	$13.17	$13.15	$13.20
Purchase #5	$239.61	11.247%	$266.5589	$266.56	$266.55	$266.60
Purchase #6	$156.48	10.816%	$173.4049	$173.40	$173.40	$173.40
Purchase #7	$81.89	4.533%	$85.6021	$85.60	$85.60	$85.60
7 purchase totals =	$779.41		$844.5633	$844.56	$844.55	$844.60