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	$224.64	7.406%	$241.2768	$241.28	$241.30	$241.30
Purchase #2	$169.72	8.595%	$184.3074	$184.31	$184.30	$184.30
Purchase #3	$160.53	5.559%	$169.4539	$169.45	$169.45	$169.50
Purchase #4	$134.61	13.390%	$152.6343	$152.63	$152.65	$152.60
Purchase #5	$162.64	7.307%	$174.5241	$174.52	$174.50	$174.50
Purchase #6	$11.82	9.380%	$12.9287	$12.93	$12.95	$12.90
Purchase #7	$211.79	5.119%	$222.6315	$222.63	$222.65	$222.60
7 purchase totals =	$1,075.75		$1,157.7567	$1,157.75	$1,157.80	$1,157.70