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	$53.33	6.791%	$56.9516	$56.95	$56.95	$57.00
Purchase #2	$64.27	13.427%	$72.8995	$72.90	$72.90	$72.90
Purchase #3	$99.91	5.690%	$105.5949	$105.59	$105.60	$105.60
Purchase #4	$86.55	9.175%	$94.491	$94.49	$94.50	$94.50
Purchase #5	$207.72	12.183%	$233.0265	$233.03	$233.05	$233.00
Purchase #6	$122.75	3.804%	$127.4194	$127.42	$127.40	$127.40
Purchase #7	$224.43	7.116%	$240.4004	$240.40	$240.40	$240.40
7 purchase totals =	$858.96		$930.7833	$930.78	$930.80	$930.80