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	$158.53	3.818%	$164.5827	$164.58	$164.60	$164.60
Purchase #2	$215.89	11.807%	$241.3801	$241.38	$241.40	$241.40
Purchase #3	$14.87	5.113%	$15.6303	$15.63	$15.65	$15.60
Purchase #4	$245.89	6.135%	$260.9754	$260.98	$261.00	$261.00
Purchase #5	$128.57	3.686%	$133.3091	$133.31	$133.30	$133.30
Purchase #6	$104.82	7.388%	$112.5641	$112.56	$112.55	$112.60
Purchase #7	$136.90	12.281%	$153.7127	$153.71	$153.70	$153.70
7 purchase totals =	$1,005.47		$1,082.1544	$1,082.15	$1,082.20	$1,082.20