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	$114.49	13.759%	$130.2427	$130.24	$130.25	$130.20
Purchase #2	$47.91	12.762%	$54.0243	$54.02	$54.00	$54.00
Purchase #3	$152.94	10.494%	$168.9895	$168.99	$169.00	$169.00
Purchase #4	$47.27	12.325%	$53.096	$53.10	$53.10	$53.10
Purchase #5	$169.41	10.479%	$187.1625	$187.16	$187.15	$187.20
Purchase #6	$92.78	7.354%	$99.603	$99.60	$99.60	$99.60
Purchase #7	$243.79	10.402%	$269.149	$269.15	$269.15	$269.10
7 purchase totals =	$868.59		$962.2670	$962.26	$962.25	$962.20