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	$85.27	5.182%	$89.6887	$89.69	$89.70	$89.70
Purchase #2	$140.74	9.489%	$154.0948	$154.09	$154.10	$154.10
Purchase #3	$81.85	10.578%	$90.5081	$90.51	$90.50	$90.50
Purchase #4	$194.28	12.291%	$218.159	$218.16	$218.15	$218.20
Purchase #5	$131.61	8.510%	$142.81	$142.81	$142.80	$142.80
Purchase #6	$162.82	7.535%	$175.0885	$175.09	$175.10	$175.10
Purchase #7	$135.72	8.692%	$147.5168	$147.52	$147.50	$147.50
7 purchase totals =	$932.29		$1,017.8659	$1,017.87	$1,017.85	$1,017.90