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	$39.45	10.451%	$43.5729	$43.57	$43.55	$43.60
Purchase #2	$89.31	7.649%	$96.1413	$96.14	$96.15	$96.10
Purchase #3	$185.97	6.855%	$198.7182	$198.72	$198.70	$198.70
Purchase #4	$125.91	9.172%	$137.4585	$137.46	$137.45	$137.50
Purchase #5	$120.92	12.770%	$136.3615	$136.36	$136.35	$136.40
Purchase #6	$134.33	6.105%	$142.5308	$142.53	$142.55	$142.50
Purchase #7	$26.80	3.313%	$27.6879	$27.69	$27.70	$27.70
7 purchase totals =	$722.69		$782.4711	$782.47	$782.45	$782.50