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	$64.27	12.138%	$72.0711	$72.07	$72.05	$72.10
Purchase #2	$159.34	8.781%	$173.3316	$173.33	$173.35	$173.30
Purchase #3	$150.95	12.269%	$169.4701	$169.47	$169.45	$169.50
Purchase #4	$200.46	8.132%	$216.7614	$216.76	$216.75	$216.80
Purchase #5	$167.25	13.801%	$190.3322	$190.33	$190.35	$190.30
Purchase #6	$186.25	12.146%	$208.8719	$208.87	$208.85	$208.90
Purchase #7	$23.55	12.308%	$26.4485	$26.45	$26.45	$26.40
7 purchase totals =	$952.07		$1,057.2868	$1,057.28	$1,057.25	$1,057.30