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	$67.61	7.154%	$72.4468	$72.45	$72.45	$72.40
Purchase #2	$104.31	11.107%	$115.8957	$115.90	$115.90	$115.90
Purchase #3	$36.62	10.720%	$40.5457	$40.55	$40.55	$40.50
Purchase #4	$42.89	8.728%	$46.6334	$46.63	$46.65	$46.60
Purchase #5	$84.97	9.534%	$93.071	$93.07	$93.05	$93.10
Purchase #6	$64.56	5.132%	$67.8732	$67.87	$67.85	$67.90
Purchase #7	$214.36	5.358%	$225.8454	$225.85	$225.85	$225.80
7 purchase totals =	$615.32		$662.3112	$662.32	$662.30	$662.20