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	$168.99	12.651%	$190.3689	$190.37	$190.35	$190.40
Purchase #2	$142.52	11.484%	$158.887	$158.89	$158.90	$158.90
Purchase #3	$156.44	6.841%	$167.1421	$167.14	$167.15	$167.10
Purchase #4	$168.41	13.534%	$191.2026	$191.20	$191.20	$191.20
Purchase #5	$174.51	13.613%	$198.266	$198.27	$198.25	$198.30
Purchase #6	$20.51	4.445%	$21.4217	$21.42	$21.40	$21.40
Purchase #7	$97.74	6.375%	$103.9709	$103.97	$103.95	$104.00
7 purchase totals =	$929.12		$1,031.2592	$1,031.26	$1,031.20	$1,031.30