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	$138.41	5.543%	$146.0821	$146.08	$146.10	$146.10
Purchase #2	$167.83	5.331%	$176.777	$176.78	$176.80	$176.80
Purchase #3	$39.71	4.377%	$41.4481	$41.45	$41.45	$41.40
Purchase #4	$81.65	4.197%	$85.0769	$85.08	$85.10	$85.10
Purchase #5	$59.89	12.195%	$67.1936	$67.19	$67.20	$67.20
Purchase #6	$240.87	4.263%	$251.1383	$251.14	$251.15	$251.10
Purchase #7	$229.73	8.418%	$249.0687	$249.07	$249.05	$249.10
7 purchase totals =	$958.09		$1,016.7847	$1,016.79	$1,016.85	$1,016.80