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	$93.34	10.314%	$102.9671	$102.97	$102.95	$103.00
Purchase #2	$196.73	13.833%	$223.9437	$223.94	$223.95	$223.90
Purchase #3	$249.89	12.570%	$281.3012	$281.30	$281.30	$281.30
Purchase #4	$160.64	7.249%	$172.2848	$172.28	$172.30	$172.30
Purchase #5	$6.37	4.780%	$6.6745	$6.67	$6.65	$6.70
Purchase #6	$190.63	6.676%	$203.3565	$203.36	$203.35	$203.40
Purchase #7	$12.34	4.536%	$12.8997	$12.90	$12.90	$12.90
7 purchase totals =	$909.94		$1,003.4275	$1,003.42	$1,003.40	$1,003.50