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	$58.66	6.500%	$62.4729	$62.47	$62.45	$62.50
Purchase #2	$196.41	9.188%	$214.4562	$214.46	$214.45	$214.50
Purchase #3	$141.76	10.278%	$156.3301	$156.33	$156.35	$156.30
Purchase #4	$143.98	4.618%	$150.629	$150.63	$150.65	$150.60
Purchase #5	$59.69	8.177%	$64.5709	$64.57	$64.55	$64.60
Purchase #6	$139.59	13.573%	$158.5366	$158.54	$158.55	$158.50
Purchase #7	$79.30	9.159%	$86.5631	$86.56	$86.55	$86.60
7 purchase totals =	$819.39		$893.5588	$893.56	$893.55	$893.60