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	$233.90	9.450%	$256.0036	$256.00	$256.00	$256.00
Purchase #2	$29.40	9.625%	$32.2298	$32.23	$32.25	$32.20
Purchase #3	$37.68	10.442%	$41.6145	$41.61	$41.60	$41.60
Purchase #4	$101.76	8.445%	$110.3536	$110.35	$110.35	$110.40
Purchase #5	$54.32	10.774%	$60.1724	$60.17	$60.15	$60.20
Purchase #6	$82.90	10.426%	$91.5432	$91.54	$91.55	$91.50
Purchase #7	$185.91	5.845%	$196.7764	$196.78	$196.80	$196.80
7 purchase totals =	$725.87		$788.6935	$788.68	$788.70	$788.70