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	$79.91	8.169%	$86.4378	$86.44	$86.45	$86.40
Purchase #2	$41.79	9.715%	$45.8499	$45.85	$45.85	$45.80
Purchase #3	$115.89	3.563%	$120.0192	$120.02	$120.00	$120.00
Purchase #4	$43.66	3.209%	$45.061	$45.06	$45.05	$45.10
Purchase #5	$169.69	11.607%	$189.3859	$189.39	$189.40	$189.40
Purchase #6	$177.84	4.673%	$186.1505	$186.15	$186.15	$186.20
Purchase #7	$198.29	12.225%	$222.531	$222.53	$222.55	$222.50
7 purchase totals =	$827.07		$895.4353	$895.44	$895.45	$895.40