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	$93.49	4.347%	$97.554	$97.55	$97.55	$97.60
Purchase #2	$233.91	3.406%	$241.877	$241.88	$241.90	$241.90
Purchase #3	$182.51	4.310%	$190.3762	$190.38	$190.40	$190.40
Purchase #4	$112.36	9.734%	$123.2971	$123.30	$123.30	$123.30
Purchase #5	$191.85	3.459%	$198.4861	$198.49	$198.50	$198.50
Purchase #6	$178.56	4.561%	$186.7041	$186.70	$186.70	$186.70
Purchase #7	$47.74	9.443%	$52.2481	$52.25	$52.25	$52.20
7 purchase totals =	$1,040.42		$1,090.5426	$1,090.55	$1,090.60	$1,090.60