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	$26.40	6.141%	$28.0212	$28.02	$28.00	$28.00
Purchase #2	$91.72	3.642%	$95.0604	$95.06	$95.05	$95.10
Purchase #3	$110.85	13.572%	$125.8946	$125.89	$125.90	$125.90
Purchase #4	$217.66	7.450%	$233.8757	$233.88	$233.90	$233.90
Purchase #5	$39.64	9.751%	$43.5053	$43.51	$43.50	$43.50
Purchase #6	$115.85	11.196%	$128.8206	$128.82	$128.80	$128.80
Purchase #7	$97.70	3.725%	$101.3393	$101.34	$101.35	$101.30
7 purchase totals =	$699.82		$756.5171	$756.52	$756.50	$756.50