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	$28.76	3.150%	$29.6659	$29.67	$29.65	$29.70
Purchase #2	$19.64	6.418%	$20.9005	$20.90	$20.90	$20.90
Purchase #3	$96.90	4.653%	$101.4088	$101.41	$101.40	$101.40
Purchase #4	$81.75	4.522%	$85.4467	$85.45	$85.45	$85.40
Purchase #5	$11.43	6.543%	$12.1779	$12.18	$12.20	$12.20
Purchase #6	$86.67	7.108%	$92.8305	$92.83	$92.85	$92.80
Purchase #7	$168.59	13.338%	$191.0765	$191.08	$191.10	$191.10
7 purchase totals =	$493.74		$533.5068	$533.52	$533.55	$533.50