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	$55.50	7.870%	$59.8679	$59.87	$59.85	$59.90
Purchase #2	$190.77	10.222%	$210.2705	$210.27	$210.25	$210.30
Purchase #3	$92.46	5.409%	$97.4612	$97.46	$97.45	$97.50
Purchase #4	$15.41	4.139%	$16.0478	$16.05	$16.05	$16.00
Purchase #5	$56.33	8.771%	$61.2707	$61.27	$61.25	$61.30
Purchase #6	$100.71	9.336%	$110.1123	$110.11	$110.10	$110.10
Purchase #7	$181.99	8.172%	$196.8622	$196.86	$196.85	$196.90
7 purchase totals =	$693.17		$751.8926	$751.89	$751.80	$752.00