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	$81.59	9.663%	$89.474	$89.47	$89.45	$89.50
Purchase #2	$158.62	11.210%	$176.4013	$176.40	$176.40	$176.40
Purchase #3	$168.88	13.866%	$192.2969	$192.30	$192.30	$192.30
Purchase #4	$78.73	13.443%	$89.3137	$89.31	$89.30	$89.30
Purchase #5	$128.91	5.860%	$136.4641	$136.46	$136.45	$136.50
Purchase #6	$154.52	12.762%	$174.2398	$174.24	$174.25	$174.20
Purchase #7	$154.74	7.525%	$166.3842	$166.38	$166.40	$166.40
7 purchase totals =	$925.99		$1,024.5740	$1,024.56	$1,024.55	$1,024.60