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	$238.43	10.544%	$263.5701	$263.57	$263.55	$263.60
Purchase #2	$204.67	5.345%	$215.6096	$215.61	$215.60	$215.60
Purchase #3	$193.96	8.478%	$210.4039	$210.40	$210.40	$210.40
Purchase #4	$79.83	13.227%	$90.3891	$90.39	$90.40	$90.40
Purchase #5	$153.92	9.834%	$169.0565	$169.06	$169.05	$169.10
Purchase #6	$125.37	5.160%	$131.8391	$131.84	$131.85	$131.80
Purchase #7	$94.41	11.424%	$105.1954	$105.20	$105.20	$105.20
7 purchase totals =	$1,090.59		$1,186.0637	$1,186.07	$1,186.05	$1,186.10