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	$160.63	3.356%	$166.0207	$166.02	$166.00	$166.00
Purchase #2	$110.63	5.206%	$116.3894	$116.39	$116.40	$116.40
Purchase #3	$30.83	5.854%	$32.6348	$32.63	$32.65	$32.60
Purchase #4	$130.54	9.686%	$143.1841	$143.18	$143.20	$143.20
Purchase #5	$188.56	3.183%	$194.5619	$194.56	$194.55	$194.60
Purchase #6	$177.74	10.485%	$196.376	$196.38	$196.40	$196.40
Purchase #7	$157.40	10.305%	$173.6201	$173.62	$173.60	$173.60
7 purchase totals =	$956.33		$1,022.7870	$1,022.78	$1,022.80	$1,022.80