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	$181.37	6.241%	$192.6893	$192.69	$192.70	$192.70
Purchase #2	$90.46	6.274%	$96.1355	$96.14	$96.15	$96.10
Purchase #3	$96.28	3.390%	$99.5439	$99.54	$99.55	$99.50
Purchase #4	$79.49	9.288%	$86.873	$86.87	$86.85	$86.90
Purchase #5	$246.70	11.830%	$275.8846	$275.88	$275.90	$275.90
Purchase #6	$59.95	6.175%	$63.6519	$63.65	$63.65	$63.70
Purchase #7	$186.82	7.409%	$200.6615	$200.66	$200.65	$200.70
7 purchase totals =	$941.07		$1,015.4397	$1,015.43	$1,015.45	$1,015.50