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	$216.77	11.546%	$241.7983	$241.80	$241.80	$241.80
Purchase #2	$181.36	9.574%	$198.7234	$198.72	$198.70	$198.70
Purchase #3	$113.76	9.572%	$124.6491	$124.65	$124.65	$124.60
Purchase #4	$136.50	11.738%	$152.5224	$152.52	$152.50	$152.50
Purchase #5	$188.58	7.657%	$203.0196	$203.02	$203.00	$203.00
Purchase #6	$54.97	7.469%	$59.0757	$59.08	$59.10	$59.10
Purchase #7	$129.32	11.426%	$144.0961	$144.10	$144.10	$144.10
7 purchase totals =	$1,021.26		$1,123.8846	$1,123.89	$1,123.85	$1,123.80