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	$67.71	13.403%	$76.7852	$76.79	$76.80	$76.80
Purchase #2	$87.53	9.568%	$95.9049	$95.90	$95.90	$95.90
Purchase #3	$100.88	13.424%	$114.4221	$114.42	$114.40	$114.40
Purchase #4	$56.72	4.411%	$59.2219	$59.22	$59.20	$59.20
Purchase #5	$185.82	10.126%	$204.6361	$204.64	$204.65	$204.60
Purchase #6	$208.30	12.284%	$233.8876	$233.89	$233.90	$233.90
Purchase #7	$200.38	10.842%	$222.1052	$222.11	$222.10	$222.10
7 purchase totals =	$907.34		$1,006.9630	$1,006.97	$1,006.95	$1,006.90