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	$80.40	6.836%	$85.8961	$85.90	$85.90	$85.90
Purchase #2	$194.94	10.649%	$215.6992	$215.70	$215.70	$215.70
Purchase #3	$53.27	12.410%	$59.8808	$59.88	$59.90	$59.90
Purchase #4	$143.75	10.810%	$159.2894	$159.29	$159.30	$159.30
Purchase #5	$147.69	4.279%	$154.0097	$154.01	$154.00	$154.00
Purchase #6	$167.71	4.403%	$175.0943	$175.09	$175.10	$175.10
Purchase #7	$180.61	7.817%	$194.7283	$194.73	$194.75	$194.70
7 purchase totals =	$968.37		$1,044.5978	$1,044.60	$1,044.65	$1,044.60