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	$207.31	7.477%	$222.8106	$222.81	$222.80	$222.80
Purchase #2	$37.56	8.178%	$40.6317	$40.63	$40.65	$40.60
Purchase #3	$118.33	3.185%	$122.0988	$122.10	$122.10	$122.10
Purchase #4	$93.36	3.164%	$96.3139	$96.31	$96.30	$96.30
Purchase #5	$153.87	5.558%	$162.4221	$162.42	$162.40	$162.40
Purchase #6	$147.58	12.129%	$165.48	$165.48	$165.50	$165.50
Purchase #7	$97.63	8.461%	$105.8905	$105.89	$105.90	$105.90
7 purchase totals =	$855.64		$915.6476	$915.64	$915.65	$915.60