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	$97.61	11.750%	$109.0792	$109.08	$109.10	$109.10
Purchase #2	$119.46	6.601%	$127.3456	$127.35	$127.35	$127.30
Purchase #3	$238.56	11.379%	$265.7057	$265.71	$265.70	$265.70
Purchase #4	$66.58	11.549%	$74.2693	$74.27	$74.25	$74.30
Purchase #5	$55.50	6.680%	$59.2074	$59.21	$59.20	$59.20
Purchase #6	$99.75	6.850%	$106.5829	$106.58	$106.60	$106.60
Purchase #7	$192.83	5.254%	$202.9613	$202.96	$202.95	$203.00
7 purchase totals =	$870.29		$945.1514	$945.16	$945.15	$945.20