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	$24.56	5.377%	$25.8806	$25.88	$25.90	$25.90
Purchase #2	$194.57	13.359%	$220.5626	$220.56	$220.55	$220.60
Purchase #3	$55.90	6.133%	$59.3283	$59.33	$59.35	$59.30
Purchase #4	$186.32	5.664%	$196.8732	$196.87	$196.85	$196.90
Purchase #5	$143.70	6.585%	$153.1626	$153.16	$153.15	$153.20
Purchase #6	$130.34	6.218%	$138.4445	$138.44	$138.45	$138.40
Purchase #7	$202.46	9.592%	$221.88	$221.88	$221.90	$221.90
7 purchase totals =	$937.85		$1,016.1318	$1,016.12	$1,016.15	$1,016.20