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	$135.36	5.602%	$142.9429	$142.94	$142.95	$142.90
Purchase #2	$40.45	12.627%	$45.5576	$45.56	$45.55	$45.60
Purchase #3	$96.36	4.685%	$100.8745	$100.87	$100.85	$100.90
Purchase #4	$137.54	4.440%	$143.6468	$143.65	$143.65	$143.60
Purchase #5	$156.71	6.563%	$166.9949	$166.99	$167.00	$167.00
Purchase #6	$168.49	3.256%	$173.976	$173.98	$174.00	$174.00
Purchase #7	$137.64	9.102%	$150.168	$150.17	$150.15	$150.20
7 purchase totals =	$872.55		$924.1607	$924.16	$924.15	$924.20