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	$187.82	4.251%	$195.8042	$195.80	$195.80	$195.80
Purchase #2	$44.83	5.603%	$47.3418	$47.34	$47.35	$47.30
Purchase #3	$111.69	5.815%	$118.1848	$118.18	$118.20	$118.20
Purchase #4	$167.47	6.799%	$178.8563	$178.86	$178.85	$178.90
Purchase #5	$16.85	6.219%	$17.8979	$17.90	$17.90	$17.90
Purchase #6	$186.87	6.260%	$198.5681	$198.57	$198.55	$198.60
Purchase #7	$72.88	13.707%	$82.8697	$82.87	$82.85	$82.90
7 purchase totals =	$788.41		$839.5228	$839.52	$839.50	$839.60