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	$233.83	12.663%	$263.4399	$263.44	$263.45	$263.40
Purchase #2	$44.78	3.802%	$46.4825	$46.48	$46.50	$46.50
Purchase #3	$87.31	6.850%	$93.2907	$93.29	$93.30	$93.30
Purchase #4	$157.89	12.832%	$178.1504	$178.15	$178.15	$178.20
Purchase #5	$186.63	9.489%	$204.3393	$204.34	$204.35	$204.30
Purchase #6	$119.76	7.647%	$128.918	$128.92	$128.90	$128.90
Purchase #7	$88.45	12.362%	$99.3842	$99.38	$99.40	$99.40
7 purchase totals =	$918.65		$1,014.0050	$1,014.00	$1,014.05	$1,014.00