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	$157.66	10.233%	$173.7933	$173.79	$173.80	$173.80
Purchase #2	$162.33	6.798%	$173.3652	$173.37	$173.35	$173.40
Purchase #3	$212.87	5.440%	$224.4501	$224.45	$224.45	$224.50
Purchase #4	$85.90	5.829%	$90.9071	$90.91	$90.90	$90.90
Purchase #5	$233.66	12.771%	$263.5007	$263.50	$263.50	$263.50
Purchase #6	$71.81	7.240%	$77.009	$77.01	$77.00	$77.00
Purchase #7	$59.63	9.690%	$65.4081	$65.41	$65.40	$65.40
7 purchase totals =	$983.86		$1,068.4335	$1,068.44	$1,068.40	$1,068.50