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	$67.88	9.571%	$74.3768	$74.38	$74.40	$74.40
Purchase #2	$102.44	12.175%	$114.9121	$114.91	$114.90	$114.90
Purchase #3	$31.58	4.277%	$32.9307	$32.93	$32.95	$32.90
Purchase #4	$89.77	6.127%	$95.2702	$95.27	$95.25	$95.30
Purchase #5	$63.45	13.709%	$72.1484	$72.15	$72.15	$72.10
Purchase #6	$33.78	5.368%	$35.5933	$35.59	$35.60	$35.60
Purchase #7	$167.43	10.407%	$184.8544	$184.85	$184.85	$184.90
7 purchase totals =	$556.33		$610.0859	$610.08	$610.10	$610.10