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	$132.77	3.417%	$137.3068	$137.31	$137.30	$137.30
Purchase #2	$184.77	6.571%	$196.9112	$196.91	$196.90	$196.90
Purchase #3	$47.48	9.795%	$52.1307	$52.13	$52.15	$52.10
Purchase #4	$116.99	7.333%	$125.5689	$125.57	$125.55	$125.60
Purchase #5	$54.90	11.241%	$61.0713	$61.07	$61.05	$61.10
Purchase #6	$39.67	4.309%	$41.3794	$41.38	$41.40	$41.40
Purchase #7	$246.98	5.476%	$260.5046	$260.50	$260.50	$260.50
7 purchase totals =	$823.56		$874.8729	$874.87	$874.85	$874.90