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	$176.89	5.400%	$186.4421	$186.44	$186.45	$186.40
Purchase #2	$152.54	7.550%	$164.0568	$164.06	$164.05	$164.10
Purchase #3	$72.27	3.539%	$74.8276	$74.83	$74.85	$74.80
Purchase #4	$148.43	9.139%	$161.995	$162.00	$162.00	$162.00
Purchase #5	$118.85	7.817%	$128.1405	$128.14	$128.15	$128.10
Purchase #6	$193.85	5.808%	$205.1088	$205.11	$205.10	$205.10
Purchase #7	$172.39	4.615%	$180.3458	$180.35	$180.35	$180.30
7 purchase totals =	$1,035.22		$1,100.9166	$1,100.93	$1,100.95	$1,100.80