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	$118.89	9.611%	$130.3165	$130.32	$130.30	$130.30
Purchase #2	$225.60	10.346%	$248.9406	$248.94	$248.95	$248.90
Purchase #3	$69.31	3.631%	$71.8266	$71.83	$71.85	$71.80
Purchase #4	$80.69	7.430%	$86.6853	$86.69	$86.70	$86.70
Purchase #5	$110.26	11.630%	$123.0832	$123.08	$123.10	$123.10
Purchase #6	$175.85	13.152%	$198.9778	$198.98	$199.00	$199.00
Purchase #7	$31.47	7.828%	$33.9335	$33.93	$33.95	$33.90
7 purchase totals =	$812.07		$893.7635	$893.77	$893.85	$893.70