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	$118.55	7.147%	$127.0228	$127.02	$127.00	$127.00
Purchase #2	$46.49	13.826%	$52.9177	$52.92	$52.90	$52.90
Purchase #3	$45.65	3.393%	$47.1989	$47.20	$47.20	$47.20
Purchase #4	$80.41	10.872%	$89.1522	$89.15	$89.15	$89.20
Purchase #5	$37.72	7.119%	$40.4053	$40.41	$40.40	$40.40
Purchase #6	$237.59	3.668%	$246.3048	$246.30	$246.30	$246.30
Purchase #7	$178.34	4.286%	$185.9837	$185.98	$186.00	$186.00
7 purchase totals =	$744.75		$788.9854	$788.98	$788.95	$789.00