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	$198.77	13.171%	$224.95	$224.95	$224.95	$225.00
Purchase #2	$89.76	3.423%	$92.8325	$92.83	$92.85	$92.80
Purchase #3	$41.98	11.701%	$46.8921	$46.89	$46.90	$46.90
Purchase #4	$249.44	6.574%	$265.8382	$265.84	$265.85	$265.80
Purchase #5	$142.31	11.368%	$158.4878	$158.49	$158.50	$158.50
Purchase #6	$142.52	9.388%	$155.8998	$155.90	$155.90	$155.90
Purchase #7	$50.71	10.673%	$56.1223	$56.12	$56.10	$56.10
7 purchase totals =	$915.49		$1,001.0227	$1,001.02	$1,001.05	$1,001.00