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	$182.43	9.792%	$200.2935	$200.29	$200.30	$200.30
Purchase #2	$59.48	5.623%	$62.8246	$62.82	$62.80	$62.80
Purchase #3	$249.50	7.361%	$267.8657	$267.87	$267.85	$267.90
Purchase #4	$99.38	11.297%	$110.607	$110.61	$110.60	$110.60
Purchase #5	$222.73	11.757%	$248.9164	$248.92	$248.90	$248.90
Purchase #6	$167.59	8.269%	$181.448	$181.45	$181.45	$181.40
Purchase #7	$133.88	7.156%	$143.4605	$143.46	$143.45	$143.50
7 purchase totals =	$1,114.99		$1,215.4157	$1,215.42	$1,215.35	$1,215.40