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	$153.69	13.612%	$174.6103	$174.61	$174.60	$174.60
Purchase #2	$207.65	12.538%	$233.6852	$233.69	$233.70	$233.70
Purchase #3	$129.83	7.326%	$139.3413	$139.34	$139.35	$139.30
Purchase #4	$102.93	6.675%	$109.8006	$109.80	$109.80	$109.80
Purchase #5	$136.27	4.336%	$142.1787	$142.18	$142.20	$142.20
Purchase #6	$61.67	6.719%	$65.8136	$65.81	$65.80	$65.80
Purchase #7	$92.40	9.198%	$100.899	$100.90	$100.90	$100.90
7 purchase totals =	$884.44		$966.3287	$966.33	$966.35	$966.30