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	$89.59	13.320%	$101.5234	$101.52	$101.50	$101.50
Purchase #2	$65.38	7.739%	$70.4398	$70.44	$70.45	$70.40
Purchase #3	$117.36	3.578%	$121.5591	$121.56	$121.55	$121.60
Purchase #4	$155.40	3.225%	$160.4117	$160.41	$160.40	$160.40
Purchase #5	$105.69	12.387%	$118.7818	$118.78	$118.80	$118.80
Purchase #6	$54.87	9.302%	$59.974	$59.97	$59.95	$60.00
Purchase #7	$230.40	4.828%	$241.5237	$241.52	$241.50	$241.50
7 purchase totals =	$818.69		$874.2135	$874.20	$874.15	$874.20