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	$34.42	8.294%	$37.2748	$37.27	$37.25	$37.30
Purchase #2	$186.61	4.211%	$194.4681	$194.47	$194.45	$194.50
Purchase #3	$116.72	3.287%	$120.5566	$120.56	$120.55	$120.60
Purchase #4	$211.59	5.616%	$223.4729	$223.47	$223.45	$223.50
Purchase #5	$237.53	4.181%	$247.4611	$247.46	$247.45	$247.50
Purchase #6	$75.87	13.666%	$86.2384	$86.24	$86.25	$86.20
Purchase #7	$163.74	7.430%	$175.9059	$175.91	$175.90	$175.90
7 purchase totals =	$1,026.48		$1,085.3778	$1,085.38	$1,085.30	$1,085.50