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	$99.73	10.640%	$110.3413	$110.34	$110.35	$110.30
Purchase #2	$217.47	12.301%	$244.221	$244.22	$244.20	$244.20
Purchase #3	$147.89	12.653%	$166.6025	$166.60	$166.60	$166.60
Purchase #4	$40.93	5.618%	$43.2294	$43.23	$43.25	$43.20
Purchase #5	$182.58	7.562%	$196.3867	$196.39	$196.40	$196.40
Purchase #6	$137.64	13.641%	$156.4155	$156.42	$156.40	$156.40
Purchase #7	$184.32	5.755%	$194.9276	$194.93	$194.95	$194.90
7 purchase totals =	$1,010.56		$1,112.1240	$1,112.13	$1,112.15	$1,112.00