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	$237.66	7.212%	$254.8	$254.80	$254.80	$254.80
Purchase #2	$155.65	8.465%	$168.8258	$168.83	$168.85	$168.80
Purchase #3	$89.62	9.219%	$97.8821	$97.88	$97.90	$97.90
Purchase #4	$129.30	4.340%	$134.9116	$134.91	$134.90	$134.90
Purchase #5	$213.77	7.544%	$229.8968	$229.90	$229.90	$229.90
Purchase #6	$171.27	4.817%	$179.5201	$179.52	$179.50	$179.50
Purchase #7	$84.60	5.413%	$89.1794	$89.18	$89.20	$89.20
7 purchase totals =	$1,081.87		$1,155.0158	$1,155.02	$1,155.05	$1,155.00