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	$6.67	8.582%	$7.2424	$7.24	$7.25	$7.20
Purchase #2	$31.42	12.498%	$35.3469	$35.35	$35.35	$35.30
Purchase #3	$26.98	9.687%	$29.5936	$29.59	$29.60	$29.60
Purchase #4	$82.69	8.747%	$89.9229	$89.92	$89.90	$89.90
Purchase #5	$100.46	8.116%	$108.6133	$108.61	$108.60	$108.60
Purchase #6	$53.25	7.423%	$57.2027	$57.20	$57.20	$57.20
Purchase #7	$36.64	3.379%	$37.8781	$37.88	$37.90	$37.90
7 purchase totals =	$338.11		$365.7999	$365.79	$365.80	$365.70