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	$92.27	13.179%	$104.4303	$104.43	$104.45	$104.40
Purchase #2	$139.42	9.287%	$152.3679	$152.37	$152.35	$152.40
Purchase #3	$47.92	12.285%	$53.807	$53.81	$53.80	$53.80
Purchase #4	$184.89	7.348%	$198.4757	$198.48	$198.50	$198.50
Purchase #5	$52.73	3.843%	$54.7564	$54.76	$54.75	$54.80
Purchase #6	$41.51	8.253%	$44.9358	$44.94	$44.95	$44.90
Purchase #7	$6.83	3.843%	$7.0925	$7.09	$7.10	$7.10
7 purchase totals =	$565.57		$615.8656	$615.88	$615.90	$615.90