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	$143.69	5.502%	$151.5958	$151.60	$151.60	$151.60
Purchase #2	$37.44	13.304%	$42.421	$42.42	$42.40	$42.40
Purchase #3	$29.81	7.295%	$31.9846	$31.98	$32.00	$32.00
Purchase #4	$108.32	7.140%	$116.054	$116.05	$116.05	$116.10
Purchase #5	$6.55	7.163%	$7.0192	$7.02	$7.00	$7.00
Purchase #6	$198.52	6.316%	$211.0585	$211.06	$211.05	$211.10
Purchase #7	$58.76	10.796%	$65.1037	$65.10	$65.10	$65.10
7 purchase totals =	$583.09		$625.2368	$625.23	$625.20	$625.30