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	$174.32	12.564%	$196.2216	$196.22	$196.20	$196.20
Purchase #2	$76.37	5.709%	$80.73	$80.73	$80.75	$80.70
Purchase #3	$126.53	9.671%	$138.7667	$138.77	$138.75	$138.80
Purchase #4	$77.80	4.260%	$81.1143	$81.11	$81.10	$81.10
Purchase #5	$166.85	4.144%	$173.7643	$173.76	$173.75	$173.80
Purchase #6	$114.52	8.180%	$123.8877	$123.89	$123.90	$123.90
Purchase #7	$153.81	4.639%	$160.9452	$160.95	$160.95	$160.90
7 purchase totals =	$890.20		$955.4298	$955.43	$955.40	$955.40