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	$134.43	5.653%	$142.0293	$142.03	$142.05	$142.00
Purchase #2	$89.70	8.412%	$97.2456	$97.25	$97.25	$97.20
Purchase #3	$110.47	11.781%	$123.4845	$123.48	$123.50	$123.50
Purchase #4	$102.39	6.848%	$109.4017	$109.40	$109.40	$109.40
Purchase #5	$211.33	5.204%	$222.3276	$222.33	$222.35	$222.30
Purchase #6	$169.72	6.153%	$180.1629	$180.16	$180.15	$180.20
Purchase #7	$23.54	10.167%	$25.9333	$25.93	$25.95	$25.90
7 purchase totals =	$841.58		$900.5849	$900.58	$900.65	$900.50