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	$173.85	12.729%	$195.9794	$195.98	$196.00	$196.00
Purchase #2	$28.91	12.411%	$32.498	$32.50	$32.50	$32.50
Purchase #3	$73.99	8.158%	$80.0261	$80.03	$80.05	$80.00
Purchase #4	$106.79	4.311%	$111.3937	$111.39	$111.40	$111.40
Purchase #5	$224.29	8.781%	$243.9849	$243.98	$244.00	$244.00
Purchase #6	$24.96	7.749%	$26.8942	$26.89	$26.90	$26.90
Purchase #7	$146.77	6.645%	$156.5229	$156.52	$156.50	$156.50
7 purchase totals =	$779.56		$847.2992	$847.29	$847.35	$847.30