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	$222.63	11.770%	$248.8336	$248.83	$248.85	$248.80
Purchase #2	$68.78	4.218%	$71.6811	$71.68	$71.70	$71.70
Purchase #3	$114.35	12.710%	$128.8839	$128.88	$128.90	$128.90
Purchase #4	$162.28	4.158%	$169.0276	$169.03	$169.05	$169.00
Purchase #5	$96.58	3.698%	$100.1515	$100.15	$100.15	$100.20
Purchase #6	$169.39	6.586%	$180.546	$180.55	$180.55	$180.50
Purchase #7	$153.64	8.586%	$166.8315	$166.83	$166.85	$166.80
7 purchase totals =	$987.65		$1,065.9552	$1,065.95	$1,066.05	$1,065.90