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	$66.54	7.773%	$71.7122	$71.71	$71.70	$71.70
Purchase #2	$119.91	12.258%	$134.6086	$134.61	$134.60	$134.60
Purchase #3	$222.76	9.675%	$244.312	$244.31	$244.30	$244.30
Purchase #4	$248.98	3.690%	$258.1674	$258.17	$258.15	$258.20
Purchase #5	$90.99	12.349%	$102.2264	$102.23	$102.25	$102.20
Purchase #6	$167.31	10.734%	$185.2691	$185.27	$185.25	$185.30
Purchase #7	$237.38	5.688%	$250.8822	$250.88	$250.90	$250.90
7 purchase totals =	$1,153.87		$1,247.1779	$1,247.18	$1,247.15	$1,247.20